I know this thread is old and was brought back up and since my previous comment I have a ton more to add. The question the OP poses is always a tough one to answer because you don't want to start a tit for tat argument however I do believe there is a definitive answer to his question. Hands down Duff's is the best in my experience. I have had every known suspension system in my shop and none of them compare to what we have done with the Duff's suspension systems now. Duff's is the only suspension company that is still working to refine and improve on their platform specially when new technology has been introduced. Combine their exceptional willingness to work with me, we have worked over the suspension systems and have a great all around driver system that is also excellent for mild off road.
The Duck Tuff system is tough to beat for most modern day enthusiasts but the system needs to be run in it's entirety to experience it as I do from the traction control, Eibach Shocks and sway bars, as well as their steering components we have taken the early bronco into and beyond what modern off the shelf equivalent vehicles can do. My bronco will handle at 100mph as well as it handles at 70mph on 35" tires. This isn't a bragging session just a reality of what it will do and with ease and most importantly comfort for both the passenger and driver. I know we are not building these to run at those high speeds but knowing they will from our testing, says a lot to me. No wander, or road creep at high speeds, just smooth and planted, not feeling of flight etc., which in the past turned out to be mild bump steer effects from the vehicle raising and lowering as you traveled giving it an uneasy squirm above 80mph and now all of that is gone with the latest steering upgrades. We have had the system off road blasting through the dunes with ease as well as mild off roading at Windrock and again within my comfort limits of what I was willing to subject my bronco too it performed flawlessly and would have probably done a lot more had I been willing to put the truck on those more challenging trails. For most of my customers it is a hands down no brainer when they go for a ride in the Duck, they simply want that feeling and handling in their bronco.
The system we developed has very repeatable results as we have found in many other builds and customers who have purchased it. Just keep in mind that springs from Deaver that some other vendors are selling are not the same Deaver made springs sold through Duff's, they both come from the same manufacturer but Duff's are proprietary and built to match the same proprietary front coils. The Eibach shocks were also designed to match this system as well and perform fantastically. This past weekend we had the opportunity to hangout in Gatlinburg with Suzy and Michael and I drove silver for the first time while Suzy drove the Duck for the first time. Silver is running long arms with single Eibacks and no sway bars and that truck handles amazingly well in the twists with no sway control because of the new shocks. Duff's has it going on for suspension control no doubt. They are not selling a system to simply build the mall crawler look, they sell a system that performs. The extra price you are paying is what it takes to have the best, they are often imitated in appearance but never duplicated in delivery of lift and performance. So when asked who's is the best, that is my answer, they set the bar and own that blue marker well. They are the only manufacturer who designs and builds their components in house, all American made and the only one who built a suspension component that did so well that race officials banned it from being used in the stock class in Baja. That says a lot for an off the shelf component that I had a hand in getting developed and proudly use on every build that rolls out of my shop.