I have made my living as an audio engineer (and now run a location recording business) and I have to say that these things are very personal. For me, ProTools is the only way to go if your main focus is audio. Jimmy is right that other solutions have the edge with certain MIDI functions, but PT has come a long way. OTOH, if you are really used to the Garageband paradigm and want to have some ability to exchange files, Logic is a good way to go. It comes with lots of decent software instruments and plugins. I do actually use it a lot for my current business because it does one thing that ProTools doesn't: bounce in faster than real time. When I do a location recording of 3+ hours, I don't want to tie my computer up for 3+ hours doing a rough mix. Logic handles mixing tasks very well. OTOH, if the work needs a lot of edits, it goes right into ProTools. For me, editing audio in Logic is, well, illogical. But at the end of the day, all the DAWs have a different feel, so if you can find a way to play around with them, it's well worth it.
I also like to encourage everyone to check out Reaper. The demo is free, the full version (which is actually the same as the demo) is dirt cheap and it's run by a company that is very responsive to the user base. Like any other DAW, there is a learning curve, but it's a very deep and capable program.