Lots of folks - even some with plenty of hours, even days of saddle time on horseback complain about a sore butt and thighs after a few hours ride time.
Same goes for saddles in trees. The butt strap is touted as more comfortable if you're up all day, the leg straps as not. I differ on this. Straps are uncomfortable, as bosin seats are, to anyone who doesn't spend much protracted time up - a little longer each day, use everyday, and muscle structure compensates.
I have been used to leg straps for every application but unfortunately I lost my Weaver sliding D back east when things went weird, had to quickly get a usefull but restrictive Butt strap Klien here to use - still using it but it sucks. Reminds me of someone needing to pee and holding their legs together. They are completely restrictive (even with a spreader hook) and the hours aloft might be easier 'cause we're sittin' on our *****, but lost mobility is the issue. Even dangerous when movement is crucial.
Don't sucker for the Butt job - in my opinion. Weaver has a low-cost legger that - if you use it enough - won't make a jack bit 'o difference to your "comfort zone" and will provide the necessary freedom to expand your abilities. A butt job won't. Even if single spar removals and gaffs dictate your work, nix the strap and what I call "lazyboy" seat. The suspenders are also something it takes getting used to. Might want to retro-fit those for later, if weight and beer drinking history is a factor for choice.
Last Tuesday I applied my new combo, you might consider this....I have an ABC nylon rock leg saddle, fitted under my Klien 'piece of junk' with the butt strap, but butt strap hangs uselessly until I might want to hook it up. Best of both. I keep the Klien because of hook-ons - 020T, lanyard w/ Petzl, spare ascender, two locking caribe's, one none, scabbard and d-handle Fanno, roll of tape, bottle of H20 in place of paint can, Prussick from Bluestreak, gym towel for sweat, and a lucky squirrel foot, stuffed.
Get the Sherrill cataloge - or on-line it. Can't beat that Weaver price ANYWHERE. The small is for non-beerdrinkers only.