I just recently started playing a 5 string and I use the b constantly. I find myself changing left hand positions to the middle of the fretboard. If the song is in c, I'll play it around the 8th fret of the e string just like I'd play it up higher. Plus I also believe that a good b string can have a Fuller sound around the 8th fret than the e string does around the 3rd. I also have small hands so I find it more comfortable. And it makes soloing a quick easy shift.
But that's just me
But that's just me
