@ beantown: yep it's a great job! Can be very rewarding.
Yep Logic is basically a MIDI sequencer which has gained a sophisticated audio side, so now both are very powerful, whereas Pro Tools is basically a great audio recorder/mixing desk, though the MIDI side was beefed up seriously in version 8, but I'm too far down the road with logic now. The good thing about Logic is that it's built for writing music and I like that. I should clarify my comment about Logics MIDI capabilities, I'm talking the way it handles not only your studio with external MIDI hardware, but also internally with MIDI data (all sequencers are basically MIDI editors) which applies to softsynths etc as well. The scope of MIDI processing available in Logic is mindblowing, from is non-destructive editing (because all the sequenced pharses are object orientated) through to complex environments which allow you to make all sorts of thing from simple arpegiators though to full on drum machines, analogue style sequencers, MIDI programmers for your hardware, etc. You can also work as Art prefers in one project file, no external hardware and yet setup a full virtual studio always ready to go. I have worked like this for years and probably 80% of my productions in the last 8 years have been software only. It's up to the end user. I run it all on a MacBook Pro, and use Mainstage live right now. Logic is setup brilliantly to be software only. The only thing I don't like are the crappy MIDI controllers on the market, which is not Logics fault. I could write a book on what you could do with Logic and many have and still not covered it all!
Have a look here for some ideas on what it can do and whether that suits you.
http://www.soundonsound.com/logic
http://www.logic-users-group.com/
http://www.logicprohelp.com/
http://www.youtube.com/results?search_query=logic+environment&aq=0
If you don't get a version of Logic straight away definitely try Garageband, as it basically is Logic soundwise with a much simpler front end (if you get Logic later you can open a GB project in Logic) and see how you like it. EDIT: and it's comes for free on every new Mac as part of iLife
At any rate whatever software you choose, I reckon you'll LOVE your macbook pro and wonder how you ever got by without it!