No!
I mean... get both.
Lol... seriously, it depends on your tastes. I like stuff the Vita has like the Ys games, dangarompa, Trails of cold stell, Tales of Hearts R, Persona 4, Zero series (though its on 3DS aswell), Fighters like MK9, Injustice, SFxT, UMvC3 and Digimon. Theres loads of less known but decent RPG's and lots of hunting games if you like that. (remember that most of the PSP library is available aswell).
The 3DS is mostly for Nintendo stuff. So, if youre into classic Zelda, pokemon and bad Fire emblem games (yeah i went there! Havent played echoes yet though.), its for you.
I got them both myself (felt the need to mention cause i'm sure a nintendo fan is gonna jump me for having an opinion and call me fanboy of something).
