You can find and buy potions that are almost as good as what you could make with the Alchemy hassle. You cannot, however, find or buy dual enchanted gear (there are a few special items with 2 enchantments, but not random loot). I can get 27% smithing gear with a store bought 25% enchanting potion. If I added in Alchemy to make a better enchanting potion, I could get 29% smithing gear. Is that really worth it? You can buy a 50% smithing potion, and I think you can Alchemy a 116% or something like that. But seriously. If you are at 100 Smithing, and using 27% times 4 pieces, you dont even need any potions, you are already going to ohko most things, and armor caps at a low 567. Alchemy has a heavy investment with very low returns. An exception to this is if you are going Destruction Mage, you can make insane +Destruction damage potions(165% I think?), which is great because Destruction damage doesn't scale.
Without any Alchemy skill or perks, I can make a 4 second paralyze 40 damage lingering health poison with Imp Stool, Canis Root, and (any lingering damage ingredient) for about 25 gold to buy the 3 ingredients. I can understand why you might use Alchemy if you specifically weren't Smithing or Enchanting anything, so that you can make powerful poisons or +One Handed%, etc, damage potions to make up for your lack of Smithed damage. I think Enchanting wins, hands down. I usually use only 2/5 or 3/5 in the first perk, and enchant with Greater souls so I don't overpower myself, but at the same time, can have access to dual enchanting.
But yeah, like most others said, personal preference, RP reasons, either are great in different circumstances to different people. Welcome to Skyrim.