Vita only. But to be honest, I spend a significant amount of my handheld gaming time on my Android Xperia and Nexus7 too. Also my girl has a 3DS that she doesn't use(she bought for NSMB, finished it and never touched it again), which I sometimes borrow for a handful of 3DS games I own(fire emblem and Miku project mirai).
I own both. The only reason i play the 3DS more is cause im playing some old DS games from my backlog but i spend alot of time on my Vita as well. --- PSN: nightwing2099 (PS3 & PS Vita) 3DS XL FC: 1693-0734-3733