Edit: is this about bouldering?
Patxi's got a couple (more?) 8c+ onsights to his name, what's his hardest RP? 9a+? 2 grades difference.I still reckon 3 grades for an all rounder.
I just did a 7c with a v7 crux.
I've never flashed 7a and I've done a few 7b+/cs. Go figure?
Interestingly (or not perhaps) my trad on-sight/headpoint difference is 0.
I'm on 4 for routes, but its probably further towards 5 than towards 3. I'm not very good at onsighting, mainly because near me I find it easier to get inspired by harder redpoints than mid-grade onsights.