The RPi will run XBMC, although the default UI is kind of sluggish just because of all the effects however, The video playback is top notch quality. I understand that you have pick a more basic scheme which is supposed to improve the experience.
I have XBMC loaded on the OUYA as well and have not done much video playing on it to compare the video quality, but the UI responsiveness is night and day different on the two devices.
I use this on my Pi and the UI is very responsive.
http://openelec.tvI have the 512MB model running at 1GHz.
