Leading the AH is pretty dangerous as it can give declarer potential discards via void/ruff. I happened to lead the singleton diamond on this hand figuring if LHO was shooting out slam, then declarer would need to have a singleton club and a singleton heart in order to make via this lead (When the ace of hearts lead would have defeated the contract). As it turned out declarer did have a singleton heart and singleton club and made. What I was considering in retrospect, what about the lead of the Ace of spades on opening lead. This only hurts on hands where partner has the singleton king or the Qx of spades and takes away declarers guess, but gives the advantage of seeing dummy and knowing if cashing the heart is right. What do you think is the long run winning, percentage lead of those two: Singleton diamond or spade Ace?