What is the difference between a ball/pin detent and friction ring impact wrench?
The pin/ball detent system is the more secure socket retention method. However they can be a real bear to release. They are especially tight when new sockets are used on a new gun. This is compounded if your hands are wet or greasy. The friction ring is still secure but lends itself to easier socket changes. So if you are going to install one socket and use it all day, over your head where it is likely to fall off the detent system is your choice. If you are using different sockets frequently where easy removal is important go with the ring retention.