I was never impressed with the studio apartment Tenpenny provides you with. For blowing up Megaton your provided with the worst residence in the whole tower which I think may actually have less living space then the Megaton house.
I like how everything is well spaced out, though, whereas with Megaton unless you avoid buying a theme you're liable to get stuck. Even without themes it's hard to sleep in that bed without Fawkes and Dogmeat occasionally blocking my way out of that room. The layout of the containers in Tenpenny isn't as nice, though - putting all those junk into a safe is a bit surreal - wish they had a locker or tool cabinet or toolbox near where the workbench goes.
In general I do prefer the Megaton house - it's more homey. I think the kitchen and fridge makes the difference. With Tenpenny I don't know where to store my food.