Revolution. Metroid, Zelda, Mario are all franchises that I love. And the news that Square Enix really approves of the direction Nintendo is going makes me think Final Fantasy might seriously jump on the Revolution bandwagon. That would just sweeten the pot.
I don't plan on buying either right now because I still have plenty of good Xbox games I've barely played. However, if I were to ever give in, I'd get the XBox 360 because I'm loyal to Xbox and Sony can suck it.