I prefer flatter fretboards generally, and the flattest I've owned was a 14" radius on a DiPinto. On four-string J-basses, I'm OK with Fender's usual 9.5" radius, but on fives a flatter fretboard is essential because I dislike reaching over a "hump" to access the E and B strings. I love my G&L M-2500 with its 12" radius, but I'd happily go with 14" or 16" on a five, maybe even flatter like some Yamahas I've tried. Plus, IME flatter fretboards allow slightly lower action, which is a plus.
