Wazzup, welcome to the forum. They both are good, and there is the potential for both to crack like any other organic material. But some Hooflex applied to horn before and during the dry seasons will take care of business. Folks do talk about horn cracks, but I've heard the experts say there isn't a whole lot of difference in frequency between the two.
My own personal bias favors rosewood. I like the way it feels when my hand gets sweaty, as it's a bit more absorbing in nature. But horn can be very beautiful and has a big following, too.
Also, you might know that cracks are from shrinkage and don't actually weaken the handles at all. I do like the way wood takes epoxy mixed with matching wood dust. And colored epoxy is also available or you can make your own. This horn vs wood thing seems to boil down to being a matter of personal taste.
Do visit often, and I hope this helps....Dan
[This message has been edited by Lt. Dan (edited 04-27-2001).]