So far I have used...
- Roku 2 XS
- Logitech Revue (Google TV)
- Western Digital TV Live
- Samsung Blu-ray
Other things being similar, 2 main differences with Roku and Revue --
Roku 2 XS comes with a motion remote with which you can play few games like angry birds (although not sure if anyone wanna play that anymore
Logitech Revue (Google TV) comes a full keyboard which makes it so easy to search stuff on youtube, plus Google TV has full browser (Chrome) -- so for those reasons, it is my fav of the others above