I'll echo everything that dzsaigirl said -- particularly about mouthpieces, braces, etc. Over the years, I've played pretty much all of the brass instruments and I would say trombone, no contest. It's just more fun. Sure trumpets have the melody, but in my opinion it is often much more fun (and more interesting and more educational musically speaking) to play the harmony, and a trombone's slide can give it fun harmony to play.
Besides, the low brass guys in the band are always a lot cooler.
