The 2 point slings such as the original leather military slings are fine. The 3 point tactical slings such as the HK, Giles, TacTaylor, and CQB are also very good slings. What I teach in our courses is that everything you do with a 2 point sling (including the hasty) you can do with a 3 point sling, and the 3 point sling offers many more options of usage that the 2 point does not . The biggest thing I have found and highly recommend is get a good quality sling either of leather or if it is nylon or some type of webbing then make sure it does not stretch.
Just my $.02
Sully
www.defensive-edge.net
Just my $.02
Sully
www.defensive-edge.net