Well, I have only used the iOS version of Garage Band and for my purposes I find it almost (not quite, but almost) useless. I've tried more than once but I just can't use it for serious work. A quick sketch but that's about it. I can't speak to the desktop version since I'm not a Mac guy.
Propellerhead Reason is a full-fledged desktop DAW and for my purposes there is almost nothing I can't do with it. For some folks, I'm sure that isn't true - if you need a lot of high-end plugins for example - but for me I can record, mix, and master MIDI and audio all in the same environment. Highly recommended.
FWIW, Cubasis on the iPad comes closest to Reason for me in terms of a "do it all" app though it does have limitations due to the hardware and from iOS.