The smaller six-strings are easier on the fingers. The E string on the bass is like playing a textured metal cable line. Cliff Burton, baby. Geezer Butler. Hell, Paul McCartney, try and get someone who can write bass lines like he did.
"Good" doesn't mean "active." The guy from Judas Priest is a great player, and he mostly hugs that bottom root. "Bad" = the guy who just copies the guitar line and doesn't merge with drummer.