Well for me it depends on what kind of hunting or shooting I'm doing. For standard hunting like deer, elk, pig or moose 10x is plenty. Especially if there's any chance of off-hand shooting. In fact, most of the time it never gets above 6x. Now if I'm prairie dog or coyote hunting I seldom go under 18x, even with 22's. For me, I figured my 204 is going to "primarily" be a bench rest gun. Even when dog hunting, 99% of the time, I'm going to be firing from a rest and even if I'm not I can still turn it down to 6x. In fact I just purchased a Nikon 4.5-14 for my new Marlin 917VSF and now I'm thinking I should of went bigger.
I always try to figure it this way. What power do I think I'm going to be running on this rifle most of the time and get a scope that starts it's power range just below that.