03 Dec 2006 at 23:50 - 13
If this is your first character, then I'd suggest a Dervish over a Ritualist. The reason is that Dervishes cause direct damage, and Ritualists either cause indirect damage or none, as they are often support characters. There is a branch of magic for Ritualists called Channeling, but it is rather weak, and not much call for Channeling Ritualists exists in Guild Wars (that is, groups will always want you to be either a summoner or a restoration ritualist).
Dervishes have a bad rap because, like Assassins before them (and warriors before assassins), most people don't know how to play them well. Played correctly, Dervishes are almost as good as warriors at surviving (tanking), and can deal more damage whilst surviving. People will probably quote you all sorts of dps calculations to prove me wrong, but I'm talking about the ability to stay alive while dealing damage, not being completely offensive.
Having said all this junk, most people find it more entertaining for their first character to press a key and watch something die (dervish), rather than pressing a key that summons something that kills the bad guy for you.