The only reason I like white better is that i can see the details better when painting.
At 6mm it's also tough to see and the white really helps the colors pop and most of my painting is already too dark.
But for my 15mm kit, I'll need to look into this more. Actually, what's there to look into, RK's done it for us.
All the pictures are taken as screenshots from my phone from his three posts, go check them out.
Black and White Test Part 1
Black and White Test Part 2
Black and White Test Part 3
I may have got these links in the wrong order. The joys of blogging from my phone. They'll get you to his site and then you can find what you need.