In reply to Michael Gordon:
> The main reason I can think of is that, with no further information given, generally 'a 6c climber' is more likely to refer to onsight, while 'an 8c climber' is more likely to refer to redpoint. So obviously a 6c onsighter is much more likely to be able to solo a 5c after practice than an 8c redpointer solo 7c after practice.
That occurred to me, but obviously not a consistent definition, so perhaps not very helpful in illustrating the difference.
EDIT: So to translate...
"An 8a+ onsight climber soloing 7c onsight is wayyyy harder than a 6c onsight climber soloing 5c onsight"
Seems more obvious if that's the intention.
> If you allow for both being defined the same way though, then the only other explanation I can come up with is that very good climbers climb much closer to their physical limit than punters.
I think that depends as much on style as grade. If you regularly redpoint then that's more likely to be true, whether it's 7c or 8c. But it's true that if you try hard, you will likely get better and climb higher grades, and that'll make you a better climber overall.
Post edited at 15:41