Great question Ray. Neither under the circumstances could be considered a military genius
William had a pretty consisent(ly bad) record elsewhere.. Steenkirke, Landen etc. The Boyne was a victory but James seemed to have a bad attack of the jitters. Up until 1688 James probably had an overall more credible military record with his involvement in the Navy etc but again, no evidence of any tactical genius.
I would probably rate William Competent or at best Skillful on the day through pure force of character. James... easy rating is to say Plodder but I think this is unfair. Probably Competent.
If I was refighting it now I'd rate 'em both the same. The roles of the subordinate commanders could be beefed up for the scenario. I would give +2 on morale for the attachment of Berwick or Sarsfield or perhaps Schomberg and William. Maybe only +1 for James.
As they say, opinions are like a s s h o l e s... everybody has one nd I am sure many will disagree with my take on it.
Enjoy it anyway and show us the pix afterwards!