The "best tactical folder" does not employ the liner lock. The best production knives in that size range are the Benchmade Axis lock (710 and the Pardue), Benchmade Pinnacle, REKAT Pioneer and Carnivore. These are the strongest and most reliable. Notice the absence of liner locks. In my opinion, the best liner lock is not as reliable as the Rolling lock or Axis lock, simple as that. The S-2 is pretty good too, but I never liked the handle to blade ratio, or the shape of the handle. If you want to spend a little more, the SpeedTech Synergy is extremely strong and precise, a little more money gets you a Sebenza. More money, and you are in the handmade integral locks and special locking mechanisms like the Sawby lock and button locks on various handmade automatics. But the value curve pretty much plateaus around the Synergy and Sebenza.
The best one for me is the Darrel Ralph large Apogee. Big, easy carrying, utterly strong and reliable, high-tech steel(CPM420V), and pretty too. Costs four times as much as an S-2 though.