I play on the PS3, I decided to buy it based upon Sony's original titles (God of War was a big deal for me), the blu ray drive, and the fact that I can play games with others without having to pay a monthly subscription. If I was uber rich, I'd have both. :)
Most of the games are the same though. Really playing a lot of Skyrim, FFXIII-2 and Amular these days. I think all are available and probably just as fun on Xbox.
As far as Dragon Age goes, the first is one of the greatest RPGs this console era, but the second is sub par at best. Hopefully 3rd will right the ship. I have a series of reviews on RPGs here, you can find more on my opinion on RPGs by going to my hubs.