I like offset sling mounts because they work well with the types of slick sided, AR-15 free float hand guards that I prefer. These hand guards typically only have a top rail and that is where I prefer to mount my light, front sight, and sling. The offset sling mount can be mounted on a top rail but it projects the sling attachment point to the side where it can be utilized with a 2 point sling.
I’ve used several of these mounts but the Low Pro Products Offset Swivel Rail Mount is likely my favorite. It’s compact on the rail and weighs only .6 ounces. Low Pro Products machines these from a single piece of aluminum. They have an integral recoil lug and rotation limited QD socket.