I think this is the key. Like a treed saddle it takes time to find the right one. It has to fit both the horse and the rider.
My trail rides rarely last more than two hours, so I’m not speaking from the point of view of an endurance rider or serious trail rider. Here’s my experience.
I used a Sensation trail/dressage that was custom made for my long legs. It was the only saddle I could find that fit Mr. Podgy. I tried many treed and treeless saddles before buying the Sensation. Like another poster said, you need a 5-point breastplate. Even then it’s not as stable as a PROPERLY fitted treed saddle. Also like another poster said invest in the right pad(s). This also takes some experimentation.
That said I think it would have been more comfortable for a shorter/lighter rider than myself. I’m 5’10" with long thigh bones. When I was competing my dressage boots were always catching on the bottom of the saddle panels, my lower leg below the belly of most horses. I gain and lose weight like everyone else. 160 lbs, plus or minus (often plus) seemed to make it a bit harder to balance than a very light rider. I also felt it somewhat a chore to post. We were both OK with the saddle and enjoyed many trail rides with no soreness afterword.
I switched back to a treed saddle when I tried a Thorowgood T 8 all purpose saddle. Originally I tried this for another hard to fit horse but thought I might as well try it on my chunky guy.
It’s a reasonably priced saddle, the seat is lovely leather but most of the saddle is a really nice synthetic very much like leather. Because it offers a lot of adjustment, girthing options and changeable gullets it fit both of us. The changeable gullets are shaped differently that the Wintec types and fit my two large shouldered horses very well. I feel very comfortable, secure and balanced in this saddle. I was over the moon when I found it fit two of my horses.
I’ve tried many treed western saddles. Personally, I’m not comfortable. I feel like I’m sitting too far back and my legs are kind of stuck. Could be the saddle fit. I’ve never tried a treeless western saddle.