Kana: You raise an interesting point: What instrumentalists "define" blues?
See, I'll be the first to admit that, as a technician, Ford is a better "guitar" player, but, even if I were to accept your assumption that "bar-band status" is somehow a deficiency (let alone its accuracy), Thackery would seem to be a better definition of Blues. I just think that his playing is more "honest." You hear more struggle and pain in his music. I think that there is a lot more polish and "correctness" in Ford's playing, which isn't such a bad thing; it's just not as down as Thackery's playing.
As far as a specific instrument "defining the blues," I just don't know if that's really what blues is about. To me, it doesn't matter if you play guitar, piano, or nose flute: if you're playing with complete honesty, you're probably playing the blues.
Again, opinions are opinions--and that's a fact ^_^
Cheers!