Once you've played the console demo, you'll realise that you're missing one really big plus on the Vita side: touch-screen! The only bit of criticism that the Eurogamer review had on the 360 version is that the bits where you were supposed to use the d-pad are now a bit perfunctory and get genuinely annoying near the end. But on the Vita, you have the touch screen as well.
And the Vita version also supports co-op. Don't know if that includes online though or only ad-hoc.But you could even say it supports same-screen co-op to some extent, because I can have my kid do all the touch work while I play with the buttons and analog sticks, or the other way around. I already popped the bubbles during his play sessions of Origins on the Vita.
And therefore the Vita also includes all the Gamepad specific levels that were originally Wii U exclusive, iirc.
So yeah, Vita version for me.
Also hope Killzone SP Campaign is good. I've always liked the Killzone campaigns so far.