Join Date: Dec 2010
Location: southern Arizona
I ride my horses in a mix of English, Australian and western. However, there are a few differences.
A western saddle typically puts you farther back on the horse, and farther back in the saddle itself, so your weight is more to the rear. When you settle back a bit, it becomes almost instinctive for the horse to bring his hind legs under him more for balance - a mild form of collection. I think this is harder to do with an English saddle, because you are farther forward, and because the narrower weight distribution would put more pressure on the horse.
Also, the English jump saddle I own is designed for a more forward style of riding. I can ride it like a western saddle, but it feels awkward. Small differences in where the stirrups hang and the seat shape can change what style of riding works best. I've never tried a dressage saddle, so nothing I write may apply to riding one. I prefer on the seat pockets for western, and just off the seat pockets for English.
Whatever style saddle you choose, I believe you should ride so the stirrup strap/fender goes straight down and your rump is in the deepest part of the seat. Depending on the saddle, that may put you in a chair seat with one and straight up/down in the other, but anything else fights gravity. In my experience, gravity wins.
Will your horse freak? Probably not. Going from western to English the first time with mine, they were more sensitive about mounting (more pressure/inch), seemed a bit puzzled at a walk, and within a few strides preferred the English saddle for a posting trot. However, for a sitting trot, they prefer the western saddle.
I go with bitless or a snaffle bit regardless, and always prefer to ride with a loose rein as the norm.