It's only advantage is it's ability to play "live" with it, in the sense that triggering pre-recorded stuff on channels is really "live." But, nonetheless, outside from that, I can't see any reason to upgrade to it instead of the new version of Cubase. Hell, do you even need to upgrade to Cubase SX3? Either way, you'll find that you can compose a track in Live just as well as you could in anything else. It's just a matter of getting there. Thus, if you're already comfortable with one thing and don't want to relearn the wheel, stick with what you know, particularly if you will only be using it as a studio tool. But, if you want to play some stuff off of a laptop for some people, you will have much more freedom than you would in Cubase.