I've been using both for three or four years now. They do make a difference in penetration. They are very tough. I agree, a passthrough is a psssthrough and a lot of shot's on deer are going to be passthrough. The skinny shafts are going to help out on marginal hits, marginal bow weight setups and also with cutting down on arrow parodox on bows not cut to or past center.
I have a friend whose son shot a doe and a buck in his first MI bow hunting season. He was using a thirty pound bear recurve at about twenty five inches of draw. The arrows were twenty eight inches, with two hundred grains of point weight and total weight around 470 grains. He was also using grizzly two blade heads. This is an EXTREMELY marginal setup, but skinny arrows were part of that successful equation. If you're shooting above fifty pounds on deer with eight to ten grains per pound arrow weight and a good broadhead design, your not going to see a difference on average shots from one arrow to another, because they're going to pass through.