We tested MN-106 (with no Assault Damage) and here's the results.
MN-106 Regular
Normal Damage (6 shots body shots to kill)
Normal Sized Aiming Reticule
MN-106 Red Dot
Normal Damage
Normal Sized Aiming Reticule
Red Dot Sights.
MN-106 CAMO
Increased Damage! (3 shots body shots to kill)
Does NOT make your name invisible
Normal Sized Aiming Reticule
MN-106 Silenced
Lowered Damage (7 shots body shots to kill)
Dramatically decreased aiming reticule (about 50-75% smaller)
Conclusion: MN-106 Regular should not be used if you have the other MN's to choose from. Red Dot offers more reliable sights. Camo offers double damage. Silenced offers a more accurate aim.
My choices?
Red Dot for long range maps (warehouse or avalanche)
Silenced for any map
Camo for short range maps (Facility or temple or jungle)