I think I'd lean toward option B - I like the idea of being part of the group that creates a new tradition of winning rather than maintaining the status quo. But I agree with those who say that in either option A or B the player has to go in focused on winning playing time, regardless of any promises and expectations.
I disagree somewhat with the premise of the question in that you can posit that all other things are equal between the two schools, but in the real world they are not. Food, girls, academics, dorms, alumni network, weather, recreational opportunities, game attendance, etc.-- they can't all be equal. Some of these are better, or at least preferable, at one school over the other. If your son doesn't know which one that is, then he needs to do more research and spend more time on campus.