Agree that you can get a million pieces of advice for this question. I run a standard MS1, just personal choice but I will not ever run a one point sling on a shotgun so I didn't need a MS4. As right hand shooter I typically do front connection on left side of gun, rear is on the right side.
For some reason on my M4 it was more comfortable to run both connection points for front and back on the left side. I have a 1301 as well so I didn't mind my M4 build being a little more on the heavy side so I think it's more a balance & LOP situation.