I am fluent in both FCP and AXP, and each has their strong and weak points. I find avid nice for fast turnaround on stories, as it seems a bit more efficient with heavy renders and complex keys. However, it crashes all the time, and i have to restart once a day at least. FCP is much more stable, and integrates so nicely with the rest of the studio, CS3, and many other apps i use. Avid requires a bit more work to integrate as well.
we use avid at work mainly because its PC & mac, and while 95% of our editors and photogs are on mac, a few still use PC.
I have used Xpress Pro, Media Composer & News Cutter, and they are all basically the same, with exceptions in network sharing and some other small tweaks. And yes, avid is much better in a networked enviroment. At the news station I do some work for, you can capture on any deck in the newsroom, and then go to any workstation and immediately drop your bin into your project without jumping through hoops. But for my personal projects I work on 100% by myself, I prefer FCP.