Both are nice resorts. The tricky part about Sapphire Valley is that part of the resort is a drive away from the recreation center. If you stayed in the units near the rec center, then I like SV. It is a twisty road drive away from Ashville, further than Lake Lure. It is about an equal toss up. Take a look at the things that you want to do, and stay in the one that is closer.
Teresa