I've heard a few good points for all sling types so I'll reiterate them here:

If you're a certain type of operator that rarely transition to a secondary then do you really care if your knees/crotch is banged up for that 2% of the time using a secondary with a one-point?

On the other hand if you're constantly on patrols where you will have the time & opertunity to transition back to your primary with a two point back slung then take that in to consideration.

Pretty much nobody uses three points anymore.

1/2 points like the ms3 magpul slings have their issues too, some people complain about them becoming unattached while in use. I don't know if the ms4 has this issue as the connection type is QD and not an alligator type clip.

Slings will vary with operation/weapon specific requirements, get the sling that applies to 80% of the circumstances you'll be using it for.