The treed vs treeless saddle debate is much like barefoot vs shoes one.. you are going to get people on both sides saying their way is the only way, and nothing you say will change their mind. Your best bet is to do your own research and listen to your horse and your body.I am very curious about treeless, but all the nay-sayers say that they aren't good at weight distribution. Those in favor of treeless say that treed saddle don't "move" with the horse and can cause poking.
We do the best that we can, I guess, but it makes me a little scared to ride....
I can tell you about my heavyweight friend Lani who has ridden thousands of miles in a treeless saddle, including 100 milers, with great success. Guess her horses didn't get the memo that only small people can ride treeless. I can also tell you about another friend who may weigh 100 pounds soaking wet whose horse will buck her off if she rides him in a treeless for more than 5 miles. Guess he didn't get the memo that treeless saddles don't poke.
If you are interested in treeless, see if you can find some in your area to try. Some saddle makers offer demo programs, so that is something else to look into. Personally, I have a harder time with treeless saddles as they don't offer as narrow a twist as a treed saddle. That wider position starts to bother my hips in time. So the horse may think the treeless is the best thing ever, but if I am riding crooked because I am hurting, that isn't going to work well in the long run. But you won't know until you try it for yourself. (And there are a lot of styles of treeless saddle around now, so may be there is one with a narrow twist that would work well even for me.)