Originally Posted by radiantm3
You're probably right as far as the paint colors mixed in. I'm just giving my comparison based on seeing both of them side by side in the sunlight. Alpine white looks more like a pure white when they are side by side. I could grab some pantone color chips to really compare whites, but I don't really care that much.
Here is a picture I took with a Alpine white 335i (on left) next to a Mineral White Metallic 335i. I think it's hard to tell the difference at a glance from a distance. The metallic flakes in MW diffuses the sun's reflection (e.g., compare the sun's reflection off the bumpers of the two cars). Up close the metallic is obvious. I've included a closeup shot of the paint next to a X-Rite color checker (18% gray) for those that want to calibrate their monitors.
Unfortunately the images here seem to get compressed significantly so quality is a lot lower than the originals.
Anyway, color is a personal choice but I liked the Mineral White better so I ordered my 2011.5 M3 Convertible in this color.