My concern about Gunks bouldering is that the few problems (with good landings) I\'ve looked at so far do not seem much like the cruxes of the Gunks 5.10s I\'ve done so far.
I agree - especially when that crux involves hanging on to work in a brassie, 15-ft above your last piece, while your leg is working like a singer sewing machine and you will your slipping fingers to stay put on delicate holds.
Strength and endurance go a long way, but I know more than a few climbers who can comfortably climb 5.12 but won\'t lead half the 10s in the gunks because they don\'t have the mental game.
I can\'t speak for anyone else, but for me, the mental game is a strength that needs to be worked in order to build, just like physical strength. Still, it does soothe the head somewhat for the muscles to report back that they\'re feeling solid, and they think they can make it to the next rest.
With that said, your anecdote about 5.12 climbers who aren\'t comfortable on all Gunks 5.10 is, I think, not just about a poor lead head. I\'ve always found that my onsight grades are lowest at the Gunks, and other places with a similar style (thin gear protected face climbing). When you\'re following a crack, no matter how hard it is, you can usually look up and figure out where the next place is you can get gear, where the next place is where you can get a good jam, or a good foot.
Often that is not so at the Gunks, where feet and hands are just white in a sea of white. Horizontals may or may not take gear, or feet, or hands. No way to tell until you get there. To me, that forces me to be much more conservative, and the grades reflect that. I suspect that I am not entirely unique in this, and it may help explain your anecdotal 5.12/5.10 climbers.
P.S. - I took the liberty of removing the backslashes from the quoted posts above, to help keep them from multiplying any further.