Now just 4's with an extended fretboard for me.
But when I was playing both, I found the B string on a 5 was the thumb-rest, but the top of the pup was the usual thumb-rest for a 4.
Funnily enough I never had any problems playing a 6. Took right to it. But that may have been the bass, a rather tasty Shuker 6 with an amazingly thin flat neck.