The area of keys for the blues is fascinating, and I think this will run and run. I haven’t got going on this yet! I’ve written a bit about this on my Facebook page. Perhaps the most interesting thing is that there are keys for chords and keys for soloing on the guitar and they don’t always coincide.
If I had to use just one key it would be E for major/Mixolydian type sequences yet I’ve never liked this key for blues soloing. I love it for other areas though and this is curious and I need to think about this and try it again. E minor type blues chords sound very dark and muddy to me. If minor blues chords are put up to A , they can sound neutral, yet they are good for theory and this is a good key for soloing.
C works for everything, and maybe it is the best key for all instrumentalists , not just guitarists ! And C minor is the most common jazz minor key for the blues.
I know a good few guitarists who like G, and there’s no doubt that jazz players ( brass, bass and keyboards) like and use F all the time, and of course they use Bb a lot. D is a good key for everything – I’ve maybe underestimated this as a key for blues on the guitar, yet I’ve always liked D minor modal sequences.