An Avenger SS would definitely be my recommendation. Most versatile/most used disc in my bag. When powered up they turn/anny/roll/hyzer flip like no other. Power them down and they will hold a frozen rope of a line or a gentle flat hyzer. Long tight wooded holes? Have no fear-the SS will cut through the trees like they're made of butter. Also very useful for stand and deliver shots especially when you can't get full power because of your lie, footing etc. They beat in nicely in esp and consistently age/cycle through the bag. I have 2 in my bag at all times and still carry the first one I bought. Too many good things about this disc to list.
I had a Cryztal Avenger SS that I was excited to try. It was fairly stable, not flippy, and I really had to force it to turn over. Are the SS's you're throwing made of X plastic? Or ESP? Maybe I was just throwing the wrong kind..?