is a hacked Vita the best way to play PS1 & PSP games on the go?
I'm thinking of getting a Slim, I have a jailbroken iPad but it's a pain in the ass to sync the BT controller and navigate the shitty Chinese emulator
a Vita I can just throw in my bag (I'm a travelling worker)
also what other cool stuff can a hacked Vita do
Honestly, if that's your only criteria, you may be better just getting a PSP or Go.
Don't get me wrong, you can play PS1 and PSP games on the Vita great, plus there's some plugins to use the second stick in some of the PSP games that makes games like MH and GTA a lot better. But overall, unless you're obsessed about the bigger screen there's no real benefit to getting the more expensive console for those two things. Vita homebrew is pretty slow going at the moment, with the most interesting just being ports of Retroarch and the like.
Vita does have a good library of games all of its own, but as I said, if it's just the PS1 and PSP games that are your focus, the PSP and Go do the job well enough for a lot cheaper.
Can't speak for every game but Ridge Racer and Soul Caliber Broken Destiny are garbage on the vita.