Combined, they make the world feel bigger and more complete. I love the Dragonborn storyline, and the island of Solstheim. (If I didn't, then
Neloth's Fine Teas wouldn't exist! Since Neloth is sort of re-introduced to players in the Dragonborn DLC.) But Solstheim is eerily beautiful, and has one of my favorite creatures, ever; the Netch. It's probably my spirit animal.
Building houses is seriously cool, as well. There's a limited amount of configuration you can do, because each wing has a limited number of functions it can serve, and that function can't just be put on another wing, but they feel like these personalized manors. I've only ever finished the house at Lakeview, Falkreath, and, while I sometimes wish I'd chosen different modules, they make perfect sense for the character I was role playing. She has a husband (who is usually out adventuring with her), a bard, a steward (who refuses to live where she was told, because of glitches), a house karl, and two kids. It made sense to me to have a kitchen, a family bedroom, and rooms above the main room for the staff, and I now wish I'd done the trophy room instead of extra storage, but what are you going to do? It makes the kids happy. ^__^
My main mage was setting up to live in the Pale, with a library and potions tower, and I believe I was assigning her the trophy room as a sort of "museum" or "research" wing. My best friend took the plot of land in Morthal. We were playing parallel Skyrims, splitting up the land for head cannon reasons, and I got Falkreath, and she took Morthal. However, it turns out Morthal is a pretty unsettling place to live. It's right outside the swamps, there are draugr and undead that crawl down the mountain, and the kids and spouse complain about how unsettling and dangerous it is. So, maybe not the best place to raise a family.
Unfortunately, my game decided to bug everything that has ever been Aela (she's the steward who won't come home), and I never got to experience the werewolf enhancements. I also haven't finished the Dawnguard storyline, but to be fair, I've never done the vanilla Dark Brotherhood, and a few other things, either, so it's really more a testament to how slow and easily distracted I am.