It's interesting to see the differences and what our reasonings are for picking one or the other style of riding.
You generally learn best what you learn first, so part of it may very well just be familiarity.
I was taught that it's necessary feel the horse under you, and that way I can usually tell what he's doing or even thinking
of doing depending on his movements, tightening of back muscles, etc. I can do that easily in English tack, but everything's completely muted in Western.
I remember when competitive trail riders in English tack were an oddity. I got a lot of laughs, reverse snobbery, and, "Hey lady, the show grounds are that
way!" thrown at me. Didn't help that I was riding an Arabian!
I rode trails for many years in a FLAT saddleseat saddle, because I couldn't afford anything else. Doing that taught me you can indeed go up and down steep hills, through water, and take any trail obstacle as long as you're determined enough and your horse is willing, regardless of the tack you use.
'Prancing Ponehs' notwithstanding, English riders are no less tough than their Western counterparts.