Yes, Mechanicalkeyboards.com is legit. They have a
vendor forum here and ShakeR, an employee of the site, is an active member here.
I think whites are a bit heavier than blues. They're smoother since they come lubed and have a dampened click. I will probably be getting these for my GH60. I also heard they're lovely if you swap out the springs for lighter ones. Blues are my favorite switches though.
Just remember if you're getting a Race, replacing the caps with a fullset is a bit hard since the layout is a bit weird. I believe the right shift is shorter than normal. But maybe someone can help me since I can't remember off the top of my head.