If you're going one or the other, Logic is the better choice. Protools may be a little better than logic for audio (and IMO that's very debatable; with the right plugins and gear you can get any kind of sound you want to), but the magnitude of difference between logic's and protools' management of audio is much less than the magnitude of difference between their sequencing abilities.
Protools audio management > logic's audio management
Logic's sequencing >>>>>>> protools' sequencing
Logic wins.
Have you used PT 8? I have both, I would say PT 8 is beating logic now in the sequencing side of things, it's real easy to edit and arrange now. IMO Logic has the better stock instruments overall along with the apple loops. The loops that come with PT 8 are ok but the apple loops are killin em!
I've used it for a very short period of time just to check it out. I actually love it a lot, but you know how it is when you've used something for so long that 'nothing beats it'. In a perfect world where I had unlimited access to Jay-Z's bank account, I would be loaded up with protools AND logic and a bunch of other gear but I think Logic is just a little better when it comes to that 'all-in-one' quality.
BTW-- do you find yourself doing projects in a series of steps where you end up using both Logic and PT in conjunction, or do you use one or the other depending on your mood and the music you're making?