They're all exactly the same. And since Braid only has 2 speeds of movement (moving or stopped) I can't imagine it being very different gameplay-wise on either platform.
I personally own the game on the Xbox 360, and think it's great! I'd probably have to suggest going with the PS3 version of the game, because the Gamepad is a nice way to layout the controls.
Braid is all about the puzzles, and art style, but the audio track is nice too, so you may want to take into account the quality of the sound system[s] you have your PC and PS3 set up with as well.
Edit:
It It might be interesting to note that on Gamespot, Braid for Xbox 360 and PS3 received a 9.2/10 critic score, where the PC game "only" recievedreceived 9.1/10. A slight difference, to be sure, but it's there.
Also, please read the comment below by 'RiMMER', as it mentions a few minor details that are different between versions. In general however, the games are wholly identical.