Well, for what I've been told, the biggest difference between the extra and edge is certain little stablity issues. The extra is a more precise design then the edge. For example, the nose on an edge will slightly wander during rolls, whereas the extra will not. How big of a difference there is, I'm not sure. I've only flown cap's and edges, and nothing over 25%. This is just what I've read and been told by others. I guess the biggest thing is to get what you like.