IMO it makes no difference. If you are going for high key and lighting the background separately then any white roll can be made to be 255 (ie absolute white) - usually by exposing 1.5-2 stops above subject.
If you want off white (popular for fashion and portraits) then the brightness of the paper is not really relevant as the distance from the light source affects its brightness.
If one is cheaper than the others I would get that.
"If I ever get satisfied, I'll have to stop. It's the frustration that drives you." - Eve Arnold