I love them. If your horse unexpectedly twists around, the poleys will force your upper thigh (and thus your hip) to stay aligned with the horse. FWIW, I regularly ride in a western, English & Australian saddle. IMHO, the most secure for a young / new rider is the Aussie. Add a grab strap, and you should be able to ride most anything out.
Some old threads with good info: Australian Saddles(aussie saddle)? Australian Saddle --> Pros/cons?