Have experienced good and bad with both English and Western saddles...not helped by a horse that has decided to put on a growth spurt and develop proper QH style muscling aged 9, for Pete's sake.
I have a top quality Walsall made English saddle, supplied by one master saddler and checked regularly by another, which suddenly started to rub this year. After studying the horse's conformation and action, both with me and the trainer (who was extremely reluctant to get on an English saddle

)this excellent saddler has taken most of the flock out of the back and tweaked the tree IN which she says defies all logic but seems to have worked.
Because of their powerful quarters and way of going, it seems to be very easy for a western trained horse to shove an English saddle forward into their shoulder, so if it's sitting there already...trouble!
Now because the horse has decided to put on yet more muscle across her loins, her lovely Westwood western saddle no longer fits

So after being saved from having to buy another English saddle we've now got to buy a new western saddle

But at least our lovely trainer sussed it out while I was still wittering around scrubbing the saddle pads thinking it was them rubbing!
Anyway, the point of this ramble is that fitting both English and Western saddles is an art, and as we have found, a moveable feast. When you've got a great saddle fitter or a trainer that can help with saddle fitting, hang onto 'em!