1. The level of psychic investment people generally put into exams at H and S is much, much greater than at Y--and I'd bet there's a pretty vast disparity in time dedicated towards the end of writing better exams as well. On the plus side, you'll probably end up knowing a bit more doctrine.
2. Again, agreed that the payoff from H is higher in the final analysis for some folks. But identifying yourself as such in advance is extraordinarily tricky. I guess it's a start if you know that you're able to write voluminously, on the spot, and cogently about matters you may have no particular concern for. But there are other variables too, some of which we've touched on.
Also, I didn't mean to imply that those who favor Yale are employing a maximin heuristic or any other method of calculation that places inordinate weight on the worst that could happen (or irrationally discounts the best possible outcomes). I think that ex ante, it's the better choice for pretty much everyone.