My theoretical experience is...
and you can take it FWIW.
My theoretical experience says the guy that has made the decision to shoot first is more likely faster, no matter if that person is the guy that the other guy has the drop on.
I attended a two day pistol course and participated in a drill with the instructor (using airsoft pistols). I had the drop on him. The demonstration had some rules. If I pulled the trigger and he did not pull his gun, I lost... otherwise whoever got their shot off first was the winner. In a half a dozen attempts I lost each and every time.
Could this be attributed to skill... possibly. However, my instructor indicated that the results were common. The person reacting to the other person is behind the curve if they are reacting to the other person.
I would no more advocate one decision in this scenario over another. I do think the exercise was illuminating that it is not so cut and dried that the person with the drop on the another person has a significant advantage.
Since I've never had this happen, I can only speak theoretically. If I did not think it likely that the guy was going to shoot me, I'd probably just give him what he wanted. Otherwise, I would draw and shoot, doing my best to get his decision making process behind the curve and reacting to me. This could involve distraction, movement, whatever.