You are right in that he has the potential to be both. But to be honest I think Shooting Guard is the way to go. To be an excellent SF in my opinion I think you need decent IS and ID (just my opinion though, many might disagree), and although the other stats are high, the time it would take to train IS and ID up to at least Strong isn't worth it when you could train JS and JR a few more pops each and be a top notch SG.
Hope that helps.