I very rarely play a 4 string any more. It's mainly 6ers now, mainly my Status S2. Were a 4 piece band with one guitar, so the 6 lets me be a bit more extravagant in places to fill out the sound a bit. I ain't no fretmelt merchant, but it suits me. So I don't really give a toss what others say.
To be honest I could get away with a 5, but I've always hankered after an S2 6er through neck with all the bells and whistles (led's front and side) and now I've got one I can't see the point in it sitting in it's case. One of the punters commented that the LED's "looked cool" through the dry ice last night apparently, we headlined a charity gig.
Besides, it seems to be a good talking point for the band as a lot of the punters don't see many 6ers.
Personally, I'd tell your singer to get stuffed. I agree with Johnson, just buy it.