I also don't recommend buying the steam version for the same reasons. (You can use the beta release of the normal one though by logging in from your email account)
Personally I'm using the PC version without any problems. I don't have any experience with Mac so far.
If Mac is faster than your PC with windows get the Mac version. Otherwise get the Windows one.
The faster the PC, the easier it will be for you to develop a game.
http://www.yoyogames.com/get here you can get Game Maker.