Is Braid on PS3/PC different in any way? Is there a definitive choice?

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.

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" received 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.

Essential Braid seems to be the same on all platforms (PC/XBox360/PS3). Same levels, same achievements (12).

I don't know about the console games, but I can add that Braid Steam version implements two useful Steamworks features:

• Steam Cloud: that allows you to store your savegames online ("in cloud") so that you can continue your worlds traverse from other PCs (or from the same if you accidentally lose data on your HDD)
• Steam Play: that allows you to play also from Mac with your digital copy

As others have said, the "standard" game should be the same on every platform, but one thing to keep in mind is that the PC version allows for playing (and building) custom levels. I have no idea how many are out there currently, but there's definitely some potential there that isn't present on the console versions.