This is my third Vita now, first was an OLED, sold it to fund getting an IPAD mini 2 retina, thought it would be better for gaming, how wrong I was, still very good for social and strategy type games, but for First person/driving/platform/sport the Vita is far better with its physical controls.
So then I bought a Slim Vita, to be honest the screen on the OLED is far nicer, OK the slim will work slightly better outside, but the whole feel of the larger OLED is nicer, for my larger hands as well, so sold it to fund getting my Flagship Xperia Z3, which i though what with this and the Ipad, no way would i miss my so called old tech PS VITA...brilliant phone, brilliant tablet, but when it comes to proper immersive gaming, the vita is miles ahead.
So I got myself another VITA OLED, that's it, sticking with it, you cant beat Uncharted, Assassins Creed, gravity rush, Killzone, loved them all, played through uncharted once, and just about to play it through again, Killzone graphics are amazing and the unique gameplay with gravity rush.
But my overall favourites are WRC 4 and the incredibly addictive Everybody's golf, just can never get bored of everybody's golf, i cant believe how long this system has been out and you can still buy lots of new funky, odd and addictive downloadable games.
As for buying physical games, places like CEX and GAME sell lots reduced and second hand at good savings.
I'm surprised Sony don't push the vita more as its such a creative handheld, the hardware inside is still more than capable and totally geared towards gaming as opposed to the likes of smartphones/tablets