When I was young and proud of what I had learned, I considered the keys of E and A as something “dull”. My aspirations rather were to play Jazz and be most versatile in all the 24 keys (12 major and 12 minor). To play in E was something very ordinary, as most of the beginners did that. So I avoided playing open strings at all.
Well, this has changed completely. Today I just love to play open strings, and I love to play in E or A (major or minor). Since I’m trying to listen more closely to what the guitar itself “wants to play”, or what one might denote as inherent in the instrument, I don’t worry any more about keys. When I improvise the respective keys define themselves without me manipulating or choosing at all. It may sound weird, but it often gives me the feeling of letting the instrument itself make the choice. After all, those “dull” chords sound just fine, and open strings can be very inspiring in various keys…
What I “found out” playing this way, was not only a preference for E and A, but another one for the key of B in the seventh position. I seems like just any electric guitar provides optimum performance there.
At least this goes for rock music – I really like the smooth feeling of keys like E flat or A flat in Jazz. These statements are only a basis for discussion, and for sure there are many more aspects to this subject, as there are down tunings, capodaster playing etc. But that’s exactly what makes playing the guitar such a great thing!