Well, if you're shooting raw, you've got the same data, so it doesn't really matter, in that you can correct it later...


But, if you've got a color cast such that something 'white' is actually using a disproportionate amount of a red or blue channel, that means that not only are you prematurely exhausting headroom in that color, but that the range of saturation, in variance to what 'white' is, will also be more limited.


I've found that many pictures I've taken that looked very poorly saturated, with very muted colors, suddenly come alive and poponce I fix the white balance towards something more 'correct', something I couldn't do by merely increasing the saturation, in part because doing so with the wrong white balance prematurely clips the individual color channels. I may want to slightly slant the white balance for effect, but if it gets far from off, it becomes close enough to impossible to fix.


Subjectively, for me, often when colors look artificially saturated, it's not just because they're too saturated, it's because one of the color channels is being clipped, and this is something that's easier to avoid when you get the white balance closer to right than not.