If I had straight Blackwood available, then I would bid that. I expect this hand to normally make 11 or 12 tricks, though 10 or 13 are possible too. Given this, I suppose the bid with the highest expected value is 5♥. We may not get to slam all the time it is right, nor will we stop short all the time that is right, but on % we will probably do better by making this call than by making any other call.