When it comes to slings, I find the expression "LESS IS MORE" very relevant. If you want your AEG to feel snugg and secure to your body, a 3 point sling provides you this in my experience. However, setting it up to your desired lenght of pull can be irritating specially when you have a very complicated sling.
However, if you want the opposite of above and if you want to be able to switch between left and right (peek around corners), which most 3 point slings prevents you from doing when worn, a single point sling is the best.
Believe me on this, as I own Eagle Assualt Slings, Blackhawk Swift 3 point slings, and Specter Gear Sling 101 and sometimes I find the features of these slings to be a nuisance more than anything else.