Hmm, Vita does look like a better value proposition now. I still have too many questions to really predict a sales winner.... like battery life. Let us also not forget that 3DS looked pretty unstoppable (remember all the "insane launch games talk?) during its coming out party. If Nintendo cuts the price by 50 dollars and bundles it (lets say with Mario Kart, although I wouldn't mind something like Pilot Wings) just in time for Vita launch, it would be a much more tempting purchase.
I think Nintendo dropped the ball by not including a second analog stick. I personally love using the thumb strap for aiming (you can still pick one up at Nintendo.com btw) but most people do not. It'll cost them the shooter crowd for sure.
Personally, I'm sticking with my 3DS.... I like Sony's 1st party, but I'll be okay only playing Uncharted on my giant HD tv. On the other hand, I would hate to miss a 2D Mario (once again, this is just me.) It's also waaaaaay too big. Love the DS form factor, it's small and portable enough to pocket, and the clamshell protects the screen. I already carry way too much on me (Tablet, Phone, etc) and the VIta would be the straw the broke the camels back. Besides, I'm not much of a playing a portable at home type of gamer. (Cafe might also prove to be a better "home portable...we'll find out soon.)