This question has been brought up quite often in the sling forum, so you may want to try there for sling questions.  

For a three point sling, I carried the Tactical Tailor 3 point for years and had no complaints.  It did everything a 3 point could do, and did it well.  It had the usual drawbacks and limitations of a 3 point sling where shooting from the support side was a chore.

I switched several months ago over to the A.S.P. Single Point Sling.  I had previously tried a box full of different single point slings, and found that while they gave greater flexibility, they weren't quite up to par with what I was looking for in a duty sling.  The configuration and build of the ASP are what make it the better beast.  The 3 waypoint link as opposed to the usual round loop allow for greater comfort, fit, and movement for me.  The tubular webbing gives greater comfort while maintaining a lower profile than the typical flat webbing, it doesn't twist, and goes on quickly.  The breaking strength is over 4000lbs IIRC for the webbing.  I've frozen the sling and hung off it, and jumped up and down on it to see if the buckles would fail, and even after 3 days in the freezer, it wouldn't slip or break.  I've switched my duty and training weapons over to use the ASP.  I truely believe it is the best single point sling available.