I agree that these 'general use' whites are the best bet as you can mount anything in them. Sure, one of the brighter or creamier hues might be marginally better for a given print, but these medium whites are by far the best average for a body of work and looking at the mounted print on the wall with nothing to compare it it, it is extremely rare to think it would look much better in anything else (with no corner samples to play with!)

Bainbridge and colormount both used to have a nice clean but not stark general white that I found perfect. Better still colourmount had this hue and a 'soft white'. If mounting a portfolio, one might select the more appropriate of the two and use that throughout. Both lovely in texture and cut nicely.