I've been watching MLB.tv, Netflix, etc., via PS3 for a couple of years now on my main TV in the living room. Worked pretty much OK, except that it was annoyingly slow to switch back and forth between cable TV and the PS3. Like if I was watching the Royals on the PS3 and following a football game on a cable station.
I recently got a Roku box to put on the bedroom TV, but first tried it on the main system in the living room.
I'm leaving it there. It switches between cable and Roku in a matter of seconds, and when I go back to the Roku, the Roku MLB software remembers I was watching a Royals game and goes directly there. With the PS3 software, I had to navigate through which game I wanted to watch, which feed, etc.
Bottom line, the Roku is much cheaper, much smaller and I recommend it highly.
(The Roku, of course, doesn't have a BluRay player, but I haven't needed that feature for some time.)