If its RPG you're into, there's Tales of the Abyss out now, Devil Survivor Overclock out now...ummm... meh, don't really know but the DS does have a whole bunch of RPGs ripe for the picking.
Of course, if you prefer pretty graphics, the Vita has...ummm... Disgaea 3 and, um.... Ragnarok Odyssey is releasing in August and there's a whole bunch of PSP RPGs available on the PS Vita store.
It all boils down to what you're looking for.
But personally, I chose to buy a Vita over rebuying a 3DS and I'm very glad of my decision. Gravity Rush is a blast and I'm on my third playthrough now.







