FYI. I currently have a Summit with their Ivory Tri Coat that is very similar to the Mineral white. I paid extra for it as well. I liked it so much I ordered it on my new X50 M-Sport. Its true that its a bit tougher to touch up but not by much.
Both white colors dont show dirt. I drove all the way from Pa to Orlando in Feb last year and it looked great in the parking lot. Oddly enough I parked with a X5 at Disney resort last year. This year I am taking the new BMW. The Summit was our family car but now the new 50i M-Sport is MY car that the family rides in.
Here are a few pics in different light of my Summit. Notice how it accents the styling lines. I believe this is why BMW used Mineral White on their show X5's.
At Disney.
in snow
long road trip to beach