Here is Brown Dominant ERDL top. Notice the shapes. They are more amoeba shaped, less sharp and tend to blend. RDF is sharp. Concise.
One of the things guys in my unit, C Co 5/14 Inf 25th ID, did in Hawaii was actually look for Brown Dominant BDUs. Especially patrol caps which invariably were never the summer weight ones. So I have lots of brown dominant BDUs which if you take into account the whole Vietnam green vs brown dominant issue for highland or lowland, the Army having no information on a difference existing that would point to one thing, manufacturer differences in patterns. So DA orders an ERDL, RDF or BDU pattern and different manufacturers produce either a more green or more brown pattern. Or you get a pattern like that Clown top where they run out of one roll of fabric and switch to another mid production.
Another thing, ERDL tends to have Loam in it versus tan with the exception of Brown Dominant ERDL. LOAM was completely removed from RDF. So its, green, black, dark brown, light brown. Confused yet?