I believe one of our first rules as hunters is to take ethical and lethal shots. Every year I find dead elk that someone wounded and did not harvest. Makes me sick. You didn't want to get into ethics, but it should be at the top of your list. Now I'm off the soap box.
I personally would take the frontal shot. But I hunt elk a lot every year, andI've been nose to nose with a Wapiti and still not had a shot! To take this shot, the animal would have to be a damn nice one. My ethical choice would be toanticipate the animals turn and judge and aim for the kill zone on the turn. You have less time to shoot than it takes to swing at a fast ball, but I know what I'm hitting when I let the arrow fly.
So, practice the shot on 3-D's if you can. Any 3-D. You'll know when the situation arises whether to shoot or not.