Logic

I would definitely not call myself a digital audiophile, so a lot of the features I don't even understand, but if I were you, I would at least start with Apple's webpage. There is a comparison page here that you can start with.

After that, I'm sure you can find some good computer audio websites by just looking in Google that will have a review of one or the other and say stuff like, "The express version is nice, but if you want to be able to do ___, you'll want the full version" etc.

Good luck.

 

Soundtrack got bundled with FCP HD.

Soundtrack is a Pro too as GrageBand is a consumer beginner tool.

 

IMO soundtrack is horrible and you're probably better off with Garageband, Logic/Logic Express are quite a bit more complex and may prove challenging at first.

 

not directly related but anyone know how logic will run on my ibook G4 1.2 ghz, 768mb ram?

Pro version lets you record an unlimited number of tracks simultaneously (providing your computer can handle it)

The express version allows for 12 at once. Check the apple website for a comparison.