Strictly from what you described, the PSP Go is what you want. The Vita is not as portable, can NOT play PS1 games to this day and has a rather poor battery life. The PSP Go can play the PS1 games you want, is way cheaper and way more portable. The battery is still poor though. The PS Vita on the other hand is future proof, somewhat, I guess :P
Edit: Also, going full digital with the Vita is very costly. I said it a thousand times already, but Sonys strategy of throwing gigabytes at you and selling memory cards for ridiculous prices is like when you are playing theme park and you turn up the salt on your french fries to sell more 20$ Cola.
Ongoing bet with think-man: He wins if MH4 releases in any shape or form on PSV in 2013, I win if it doesn't.
