I have the MCR4 while my friend went with a MCR7.
The differences I have noticed is I have more molle in the front area, where he has lost a few columns due to the quick release in the center. Your choice.
I also use the hydration option that integrates it into the MCR4 and also the MCR7. Much better than hanging a separate hydration pack to your back.
http://www.airsoftoutletnw.com/condo...ration-carrier