OMG, a religious argument.....
I have both, and use both, but there sure seems to be pretty strong opinions on both sides. The Xikar fits my hand very well, and I like it a lot. The Palio is a very sharp, very nice cutter as well; honestly, either should last a lifetime and it's more a personal preference than anything.
One bit of advice I'll offer is no matter what you have for a cutter, you need to clean them every so often. I picked up a pack of alcohol wipes at the pharmacy and they are "the bomb" for this job. What happens is that over time, tobacco oils coat the blades and cutting surfaces, making them appear dull and providing a lousy cut. Clean, either of these cutters should last more than a lifetime, but dirty, neither will do the job satisfactorily.
Cheers - B.B.S.