Well I received the M&R 40" bar yesterday and I must say initial quality is impressive. Nicely built bar very similar to my Rigid.
Not knocking one of the other but here are the physical differences:
As far as appearance wise, the main noticable difference is the M&R has more of a chrome/reflector look to it just due to the fact that the LED modules are more flat than Rigids. The Rigid has a larger "dip in" towards the LED light itself. The only other differences are that the screws that hold the chrome/mirrored LED module into place are a little more larger and more noticable on the M&R and the actual LED doesnt have a "dome cap" over them like the Rigids do. The fact that the "dome cap" is missing sort of creates a yellow effect.
All of that is purely cosmetic. A vs B.
The real test shortly.... fired up.
Pics:
M&R top/left
Rigid bottom/right