Hello fellow 7 string players. I primarily play jazz and have recently added the 7 string to my studies. It seems that most jazzers tune the extra string to A below the low E string. This is a curious choice as it brackets the low E string with a pair of A's an octave apart.
Rock players typically tune the added low string to B, a 1/4th below the low E. This make it symmetrical with the spacing of all the other string intervals (except of course the G to B string interval) This means you can pick up a chord with a 6th string root and simply move everything over a string and you will have a chord a fourth below the one you started out with (compensating of course if you are moving a finger off of or onto the B string) This seems to be a much more reasonable approach than the asymmetric low A arrangement in which you just have another copy of whatever was happening on the other A string.
Can someone explain to me the reasoning behind why jazz players prefer the low A tuning and not the low B arrangement?