BOTH! Let the nut be the nut if it's more comfortable to play there and let the 5th fret be the nut when that's easier for you! The key of Eb or D has to be a pain in first position.... and are much easier to access off the B string and Eb was used allot by Hendrix, SRV, Stevie Wonder....etc. I mean I wouldn't abandon first position,
I would add 5th position.
peace

tjm