Well, check me if I'm wrong, but in addition to coming with clips and samples and what not, GarageBand is still a full-featured multitrack recorder, right? So, if you import your own drum loops or
drum tracks and record your own gutiars and bass, then it won't sound any less "original" than any other editor?
I mean, GarageBand isn't the most robust recording platform out there, but if you're looking to learn on a budget, "free" is tough to beat. Save your cash for a Shure SM57 and a mic stand, and go with Garage Band.