If you just want to do endurance to have fun, about any breed with enough conditioning can do it. I ride with Quarters, Walkers, Paints and about any cross you can name of. If you want to do endurance and be competitive, it is far easier on an Arab. They are just made for it. Arab crosses are great also. I rode a Quarter starting out and I didn't really enjoy getting a butt kicking everytime I rode. I wanted to do better, so I converted to an Arab. Now I love them. I have three, two full blooded and one cross. The full blooded mare is by far the best one. She is just made for endurance and she loves it.