I overlaid the pattern from different photos in a couple places, and sort of loosely painted in bits in other sections as needed. If you look closely you'll see areas that don't have the pattern, like around his left arm and parts where the wrinkles were more important to show. Leaving the pattern out of those parts allows the viewer to see the shape better (from wrinkles) and also the overall color you want them to see. The mind fills in the pattern. If I were to make the pattern as dense and high contrast as it actually is in all places, it would be too 'busy' looking and some of the shapes and form would be lost. Hope that helps!
Just a preference, and I haven't seen much in other patterns that make it more effective than multicam. I know that a lot of units who have the option of what to use are using it, so it seemed a somewhat logical choice if the Marines were switching patterns. I'm sure it would depend largely on where Marines were active though. Hope that answers your question!