To add to ^^^, that is one factor to consider. I honestly felt like the white wasn't overly glossy, and it felt and looks more like paint on a car to me. They're both plastic - and I felt the matte finish gave it a more silicon case look, which I hate -- but I seem to be alone on that opinion, as everyone loves the soft touch.
I never handled a live black model though....just the dummy versions - so maybe the material is better/more grippy on the live versions? That's a question nobody has been able to answer me for sure.
Another advantage I discovered after my white was dropped onto concrete is that it took the impact really well and markings were minimal. From the faint scratches that did remain, I was able to buff them out almost entirely with Meguairs scratch X....not sure you could do that with a matte finish.
Bottom line is go with black if you like the matte look, want a classic business look, or just like black in general. Go with white if you want the phone to stand out more, prefer contrasting colors, or think anything I said above has any weight.