Psiberzerker
Author
Well, since I confused everyone by focussing on @H in my fist post, let me detail all the ways that 1H is nominally superior that 2. Again, this is purely min-maxing for DPS, while Damage per Strike (Instead of Second, or Speed) is generally higher with 2H.
First up, you can have 2 of them. This means to take advantage of it, you pretty much have to Dual Wield, and say goodby to Block. You can always drop in a shield, if Dual Power Attach after Dual Power Attach gets old, and it's just that king of fight. However, you lose your Dual Flurry/Savagery bonuses, and if you Block at all, you lose your DPS advantage. However, you gain low stamina Stagger, and all the great things in Block, the greatest of which is Elemental Protection, which requires a Shield.
This is the ultimate advantage of 1H. If you perk out that Tree, Block, Destruction, and so on, you can Spellsword, Hack&Bash, or Dual Flurry for wide open Melees, duels with big stompies, and static damage races. (You can also Bash&Burn with a Shield/Spell combo on the same build.) 2H gives you 2H, Bash (Half of Block) and that's it, unless you swap out to something else. Also, the Drawing animation is very slow, on top of retarded running, high Stamina drain from such a heavy weapon, and slow striking speed.
As DarthSpecturm pointed out, Enchantments, and Smithing Improvements are not only multiplied by dual Wielding, but Striking Speed. If you put 15 points of Absorb Health on a Dagger, and a Greatsword, you will hit 3 times to every one with the Dagger/Greatsword. Doesn't matter which material, or smithing tier, all else being equal, you will proc these effects more often with 1H, and double that with DW. (If you use double Power/Attacks.) Dual Flurry just enhances this more, though Elemental Fury only works with weapons that aren't technically Enchanted. (Windshear's Stagger, the Bleed DoT from perked Haxes, the Ebony Blade, and a few others.) Bleed/Burn is particularly effective this way, because each DoT effect stacks, so you can keep piling them on until it's doing more DPS than your Strikes!
Looking at it that way, it appears that Daggers are the most effective weapons possible. However, there's some minor glitches that make this less than so. For instance, Daggers aren't affected by all 1H Perks, Potions, and don't have specialized perks that can further enhance damage. However, if you're just going to Double Attack, daggers (Not counting the Blade of Woe, which swings at Sword speed) in the off-hand give you the fastest Double Attacks, and Dual Flurries. Therefore, you can have a Mace in the primary hand, and just for these two techniques, it will strike just as fast. Also, when you Dual Power Attack (I just say Dual Flurry for short) with a Dagger in the primary hand, there's a grip switch added to the animation which adds a small delay. It's not much, but as it's slower than doing the same thing with a Sword, which does more damage, this strike does significantly less DPS with a primary sword than a dagger. (I have to assume this is intentional.) I prefer a Dagger/Handaxe combo to stack up Hack&Slash bleeding as quickly as possible, either with Elemental Flurry, or a Fire Enchantment to stack on Burning DoT. This is literally the fastest way to kill off anything that's not immune to either effect. (Draugr don't Bleed, but the Burning does more damage to compensate.)
Now, the reasons why I usually go with Blades Sword/Skyforge Steel Handaxe instead is because 1) Sword/Axe makes both of them strike at the same speed, so I can chose one, or the other every attack. It's usually the Axe, because of the bleed, but the Sword is better for Reach with the left hand Power Attack, to make up for the short reach on the hatchet. 2) Both are Steel Tier, so with 1 Perk, and about 31 Smithing, I can get both up to Superior (In 1 crafting session so I don't have to do it again) while they both do more damage than either regular Steel Weapons. 3) with Bleed, and Critical perks, I can enhance both of their damages, and 4) There's more good Enchanted Swords in the game than any other, for upgrades. So, I can grab Windshear for Staggering offhand attacks that don't use stamina (Hack, and Slash with the effect of Hack, and Bash, regular attacks, and higher damage in both hands! Plus Bleed/Crit.) The Drainheart Sword for infinispin, each Dual Flurry recovers stamina so you can do it again, and again, and again until you have to stop, and recharge,or swap for one that isn't dead. (You can get a stack of them, and they're dagger light, though not speed.) The Nightingale Blade I shouldn't have to explain. Drain Health, and Stamina on a stick, only heavier, and up to Daedric damage without Smithing. (Or you can smith it up with 5 less Stamina Drain, and 1 less Base Damage. Leveled Item.)
Unfortunately, there's no scripted handaxes with a decent Enchantment. Sorry, you pretty much have to DiY, find one in Random Loot, or be satisfied with "Just" bleed damage (Which is plenty for me.) Regardless, once you dial into Sword/Axe, the timing and DPS are about optimal. I usually just stick with the starter set, Tachi, Hatchet, Armsman(1-5), Critical Strike91-3) H&S(1-3) Fighting Stance, and Critical Charge handle all the power curve up to OP, once I get the initial Smithing out of the way. Both can be gotten up to equivalent to Ebony with 1 Perk, and 31 Smithing, and unenchanted, you can use Dual Flurry.
If I'm an Assassin, I swap between those, Windshear, and Valdir's Lucky Dagger. Still Steel, but faster, and you can still proc Assassin's Blade offhand, then stand up to stunlock everything to death with Crits popping off like corn.
First up, you can have 2 of them. This means to take advantage of it, you pretty much have to Dual Wield, and say goodby to Block. You can always drop in a shield, if Dual Power Attach after Dual Power Attach gets old, and it's just that king of fight. However, you lose your Dual Flurry/Savagery bonuses, and if you Block at all, you lose your DPS advantage. However, you gain low stamina Stagger, and all the great things in Block, the greatest of which is Elemental Protection, which requires a Shield.
This is the ultimate advantage of 1H. If you perk out that Tree, Block, Destruction, and so on, you can Spellsword, Hack&Bash, or Dual Flurry for wide open Melees, duels with big stompies, and static damage races. (You can also Bash&Burn with a Shield/Spell combo on the same build.) 2H gives you 2H, Bash (Half of Block) and that's it, unless you swap out to something else. Also, the Drawing animation is very slow, on top of retarded running, high Stamina drain from such a heavy weapon, and slow striking speed.
As DarthSpecturm pointed out, Enchantments, and Smithing Improvements are not only multiplied by dual Wielding, but Striking Speed. If you put 15 points of Absorb Health on a Dagger, and a Greatsword, you will hit 3 times to every one with the Dagger/Greatsword. Doesn't matter which material, or smithing tier, all else being equal, you will proc these effects more often with 1H, and double that with DW. (If you use double Power/Attacks.) Dual Flurry just enhances this more, though Elemental Fury only works with weapons that aren't technically Enchanted. (Windshear's Stagger, the Bleed DoT from perked Haxes, the Ebony Blade, and a few others.) Bleed/Burn is particularly effective this way, because each DoT effect stacks, so you can keep piling them on until it's doing more DPS than your Strikes!
Looking at it that way, it appears that Daggers are the most effective weapons possible. However, there's some minor glitches that make this less than so. For instance, Daggers aren't affected by all 1H Perks, Potions, and don't have specialized perks that can further enhance damage. However, if you're just going to Double Attack, daggers (Not counting the Blade of Woe, which swings at Sword speed) in the off-hand give you the fastest Double Attacks, and Dual Flurries. Therefore, you can have a Mace in the primary hand, and just for these two techniques, it will strike just as fast. Also, when you Dual Power Attack (I just say Dual Flurry for short) with a Dagger in the primary hand, there's a grip switch added to the animation which adds a small delay. It's not much, but as it's slower than doing the same thing with a Sword, which does more damage, this strike does significantly less DPS with a primary sword than a dagger. (I have to assume this is intentional.) I prefer a Dagger/Handaxe combo to stack up Hack&Slash bleeding as quickly as possible, either with Elemental Flurry, or a Fire Enchantment to stack on Burning DoT. This is literally the fastest way to kill off anything that's not immune to either effect. (Draugr don't Bleed, but the Burning does more damage to compensate.)
Now, the reasons why I usually go with Blades Sword/Skyforge Steel Handaxe instead is because 1) Sword/Axe makes both of them strike at the same speed, so I can chose one, or the other every attack. It's usually the Axe, because of the bleed, but the Sword is better for Reach with the left hand Power Attack, to make up for the short reach on the hatchet. 2) Both are Steel Tier, so with 1 Perk, and about 31 Smithing, I can get both up to Superior (In 1 crafting session so I don't have to do it again) while they both do more damage than either regular Steel Weapons. 3) with Bleed, and Critical perks, I can enhance both of their damages, and 4) There's more good Enchanted Swords in the game than any other, for upgrades. So, I can grab Windshear for Staggering offhand attacks that don't use stamina (Hack, and Slash with the effect of Hack, and Bash, regular attacks, and higher damage in both hands! Plus Bleed/Crit.) The Drainheart Sword for infinispin, each Dual Flurry recovers stamina so you can do it again, and again, and again until you have to stop, and recharge,or swap for one that isn't dead. (You can get a stack of them, and they're dagger light, though not speed.) The Nightingale Blade I shouldn't have to explain. Drain Health, and Stamina on a stick, only heavier, and up to Daedric damage without Smithing. (Or you can smith it up with 5 less Stamina Drain, and 1 less Base Damage. Leveled Item.)
Unfortunately, there's no scripted handaxes with a decent Enchantment. Sorry, you pretty much have to DiY, find one in Random Loot, or be satisfied with "Just" bleed damage (Which is plenty for me.) Regardless, once you dial into Sword/Axe, the timing and DPS are about optimal. I usually just stick with the starter set, Tachi, Hatchet, Armsman(1-5), Critical Strike91-3) H&S(1-3) Fighting Stance, and Critical Charge handle all the power curve up to OP, once I get the initial Smithing out of the way. Both can be gotten up to equivalent to Ebony with 1 Perk, and 31 Smithing, and unenchanted, you can use Dual Flurry.
If I'm an Assassin, I swap between those, Windshear, and Valdir's Lucky Dagger. Still Steel, but faster, and you can still proc Assassin's Blade offhand, then stand up to stunlock everything to death with Crits popping off like corn.