As others have said, for me it all depends on the material. My current original band plays something like classic rock, and while a few tracks benefit from the B string, I've played almost all gigs on my fours, and can just switch back and forth.
Before this, I didn't have a five, and I played in a band whose songwriter liked E flat, G sharp, etc., and a five would have been extremely useful. I got by using fours with a drop tuner because I didn't need any notes below low D, but a B string would have made some parts easier, and possibly led to creation of more interesting parts in some tracks. That experience is largely why I bought a five.
Since getting a five, I've also played two rock musicals, in which the B string has been essential.
Before this, I didn't have a five, and I played in a band whose songwriter liked E flat, G sharp, etc., and a five would have been extremely useful. I got by using fours with a drop tuner because I didn't need any notes below low D, but a B string would have made some parts easier, and possibly led to creation of more interesting parts in some tracks. That experience is largely why I bought a five.
Since getting a five, I've also played two rock musicals, in which the B string has been essential.