I have Kings as well, but if money were no object I probably would have gotten Fox. The DSC adjusters are nicer and more functional than what comes with Kings and this is just my opinion, but I feel like Fox has done more R&D for the 4Runner specifically. King has tons of racing heritage, but Fox designed the suspension that comes on TRD Pros so I would imagine they have a pretty good idea of what works on the 4Runner.
Unfortunately, a full Fox 2.5 with DSC was almost $1k more than what I got my Kings for so that made the decision for me. I also couldn't buy the Fox direct from factory with heavier springs - I had to order additional heavier springs then pay to have them installed, which made it even more expensive.