I prefer leather. I've found that synthetic saddles tend to give me sores from rubbing. I love how light they are and they're easy to clean. However, I'll stick with leather.
I use both. I like the Synthetic for jumping. The Wintec Equileather is super "sticky" hehe. And same with the equisuede. I love how is wears, or doesn't!
I love my leather dressage saddle, looks so beautiful and feels good. It can be a little slippery after I clean it though, hehe.