M2 Beach is only about 750 feet net downhill. It starts around at about 750 feet. The first couple miles are uphill and you go up to about 930 feet and end at sea level.
It is a gradual downhill course. I don't really understand how it is only 750 feet downhill since it seems downhill the entire way from 3 to 23 with one hill.
It is not one of those 4000 feet downhill Revel courses that I would agree would end up not being as fast as some may think because quads can only take so much pounding. If you are really light and small those Revel courses might be good for fast times.
El Paso looks like it has a good uphill past 21 miles in. I could see that slowing down a lot of runners. That course looks like it rolls mostly and has longer downhill sections. It doesn't look that fast of a downhill course.
I think something like the M2 Beach course is about as fast a course as you can find.