Degrees of bounce represent how your wedge performs as it makes contact with the surface you're hitting from. For instance - if you play most of your golf on firmer fairways, or per chance are playing a course that has little-to-no sand in the green-side bunkers - you'd probably fair better with a low-bounce option. Same for hardpan lies and the like. Lower bounce degrees means less "bounce" off the surface and more "digging." I would say anything less than 8 degrees (maybe even 8 degrees in some cases) would be considered low-bounce. I think(*) the lowest degree of bounce that any manufacture makes is 4 degrees, and most likely you'll have to special order that one.
So obviously more degrees of bounce is just the opposite. If you're playing on normal surfaces, as in not too firm nor too soft) I would think something around 12 degrees would be fairly standard. And too - 12 degrees would probably be fine with soft conditions too.
Sand consistency in the green-side bunkers and the softness or firmness of the surfaces you play most often should really be the determining factor.
Now what really sucks is when you've got soft conditions (or normal conditions) as far as turf, but then have little-to-no sand in your green-side bunkers... because you don't want the low-bounce option for the softer surfaces, because obviously a low-bounce wedge will dig into the surface more. But you do want the lower bounce for those almost bare lies in the green-side bunkers. So that obviously creates a dilemma and will force you to compromise somewhere.