Call it lack of discipline on my part, but based on experience with a lot of different sights and hunting and many (too many?) years around hunters and listening to excuses there's a problem with full buckhorns if you don't watch out when you're under stress. For me anyway, and I suspect for lots of other hunters based on misses.
When light is low or you are under stress, you'll tend to pull that front sight up a bit to see it better. High shot every time. It gets worse with a full buckhorn, because your eye will try to treat it like a big ole peep sight.
If you want to test it, shoot with someone who has full buckhorns and do a rapid fire test or figure out some other way to put stress on the shooting. All their misses are going to be high.
Full buckhorns look cool, but I won't have them on any of my rifles that I'll hunt with. Maybe just me and my own problems, but I've seen enough to convince me I'm not all on my lonesome with this one, no matter what the other shooters claim.