I also find that for distance riding I want a saddle that helps keep me secure even when I’m fatigued. This is why I originally switched to an endurance model, because of a problem in my hip that allows my leg to swing after the first few miles if it doesn’t have help. The western-style endurance saddle (Abetta) I first got was great for supporting the weak leg and hip because of the wide fender (I turned the stirrups to prevent knee pain). And the seat is great for hills–takes less effort to stay in it during the surges you get when going uphill. This doesn’t mean much in the first few miles, but toward the end of the ride, it is nice to have help from the saddle.
Now I ride in a Bob Marshall treeless endurance saddle. Again, it looks a bit western, with swells and a deep cantle (no horn). The stirrups attach low on the skirt, which helps distribute the pressure for those of us who ride heavy in the stirrups.
This is another problem with some non-distance saddles: lack of distribution of stirrup pressure. Some of us ride two-point a lot, or at least ride heavy in the stirrups. Some endurance saddles are designed to spread out the pressure from the stirrups, either by splitting the leathers or attaching them low. This is an important consideration for your horse’s back comfort when choosing a saddle. It isn’t an issue for every rider, but it was for me.
I agree with G, in that it is more important to have a saddle that fits your horse well than it is to get a specific model for a specific use. Endurance riders are in the saddle for hours, so any small discomfort becomes magnified, which can lead to swelling and sometimes lameness. I’ve seen plenty of short-strided horses at the end of an endurance ride who cringe when the vet even runs his hands across the back. That’s sad. After fit comes rider comfort. Then you look at each model, test ride, and see what works best for you and will still be comfortable after 5 or so hours of riding uneven trails and hills. Plus, it helps to have numerous sturdy rings to hang your gear. Breastplate and crupper attachments are a real plus, too.