I've been reading praise for Garage Band on the Mac for years but in my work life I have to use PC so I never got to try it. They now make Garage Band for PC so I'm giving it a try. I get the feeling it is aimed at the less experienced home recording aficionado but since that is me, that's okay
From what I've seen so far it looks like it will meet my immediate needs.
Re: Mac Vs PC: Traditionally PCs were marketed to the business community and Macs to the artistic creative niche. While Macs still appear to have an edge on the number of products for the artist I see that gap closing fast. I see no point in spending the money on a good Mac when I already have a good PC and the selection of composing and recording tools for PC continues to grow. Plus the technology of Virtual Machines is getting to the point where it is or soon will be feasible to run a virtual Mac OS on your PC and have the best of both worlds. I already run a virtual Mac for some less resource intensive software. A state of the art PC could probably run all of the recommended Mac apps in a virtual Mac OS environment with no problem.
Good luck. Let us know what you decide and how it works out once you know.