As someone who just last year at this time decided to switch (almost completely) from English (H/J, Dressage, Fox Hunting, Side Saddle, saddle seat) to Western (Ranch Riding, but aspire to low level reining and cow work) --I can tell you there is a whopping-lot of difference.
For me, biggest difficulty is my seat (posture in the saddle) --I am constantly reminded by my very successful and excellent trainer Savannah White https://www.facebook.com/savannah.white.7545 To “sit on my pockets.” As a long time fox hunter, I have a preference for a bit of a “chair seat.” Nope, not riding my Western trained horse Bob. That puts too much weight on his forehand which he needs lighter for what we do.
Next is hands: Bob rides on a “looped” rein --not quite as looped as Western Pleasure, but still not contact with the bit. Bob knows what to do from my legs and seat --and (almost never) my hands --except for slight left to right movement sometimes a lift to cue tighter turns --like a spin (although Bob does not spin, he does an absolutely correct turn, just not as fast as a true spin).
Some issues with shoulders --need to be straight but maybe sightly behind the vertical --definitely NOT leaning forward EXCEPT to cue an extended trot or canter --then Bob lengthens his stride.
Head is about the same --chin up, looking where I’m going.
Hand is always low enough that my little finger can touch Bob’s mane.
Feet, back more of a straight leg, although in Dressage I rode with a nearly straight leg too. Definitely longer leg than I ever rode H/J or fox hunting --OH --if I am truly roping (don’t know that I will ever get that far) or cutting, I need to take my stirrups up one more hole.
I always wear spurs, although I rarely need them -Bob pretty much moves off calf pressure.
As to why calf-roping? As much a tradition as Fox Hunting —I always hunted live with only a few drag hunts in my many years. At my level and gender, I aspire to do “break away” roping --my rope has a plastic piece that, should I ever actually rope a live critter, the break away hondo separates --no harm to critter.
And as to trail riding? I do that generally in my Western saddle regardless of what horse I take --it is easier to mount (I’m old) using the horn.
And one last thing: WP --my Granddaughter loved Western Pleasure --what I learned watching her for 10 years was that the best WP horses are bred for the job and have a low head carriage from the time they are born. Second, the training is no more “cruel” than what I have personally seen in the dressage ring. Every discipline has its bad apples, but the kids who rode WP with my granddaughter loved their WP horses and cared for them every bit as much as the kids who ride English. I have ridden her WP horse (sadly he died at 26 last June) and frankly, that slow canter is s m o o t h! I can easily see why some people prefer to ride WP. In all honesty, I’d ride her WP horse any day of the week over the contesting horses that have to be blind folded to lead into the ring. Every discipline has its bad apples --as I said.