I have used both systems for years, nearly any type of program that you can run on windows you can you can find and equivalent for on Mac. The nice thing about todays intel based mac's is that you can "dual boot" both windows and Mac OS on the same machine so if there is that one windows program that you just have to have you can use it when need be but still have the security and piece of mind running mac os for day to day uses. With out knowing exactly what you intend to use it for its hard to give specific recommendations on which mac I would recommend however generally speaking for just general computing the
imac is a good choice for the user not looking for lots of horsepower on the desktop side, and the mac book on the notebook side, stay away from the macbook air
IMO its just a status symbol and not suited to be a primary machine. If you are looking for a little more power or want to get into graphics, audio, or video editing the mac book pro's and mac pro desktops are what I would recommend you look at. All of this is just my opinion and I'm sure I left something out that someone else will fill in for me.
And welcome to the dark side
