(wow, Kurt Rosenwinkel and Bill Frisell, two names I never expected to see on this forum! I'm not sure how I'd rate them specifically on guitar tone, don't think about that much other than liking theirs, but as musicians and composers, these are the two guitarists I would put at the top of my personal list today, possibly with the nod to Rosenwinkel for his creativity, but that's a tough call.)