Join Date: Aug 2009
Location: New South Wales, Australia
As others have said, totally different saddles. If you're not going to be jumping much I'd probably lean towards the Isabell. However, it's my experience with the Isabell that people either love it or hate it, it's not the kind of saddle everyone likes so you really need to sit in it to see what you think.
To be honest, I'd always go a dressage saddle over an AP. While you can have good alignment in the AP it doesn't particularly encourage it, where as the dressage saddles do (and in my opinion are more comfortable).
Things to look for in an English saddle - first up horse fit. Even with gullet change systems and reflocking Wintecs don't fit every horse.
Second rider fit. You can get narrow and wide twist English saddles which is just a matter of personal preference. You need the leg panel to be the right length and width for you (dressage saddles straight cut - close contact forward). There are variates in seat depth (dressage deepest - Close contact shallowest) and the stirrup bar can also placed in slightly different locations. If possible, get a saddle fitter or saddle shop to bring out a range of saddles for you to ride in, it's the best way to do it.