I have a set of King 2.5's from Accu-Tune with their custom Adventure Tune on the way. After talking it over with a few friends that have both I felt like the Kings were the way for me to go for a couple of reasons. 1)They are cheaper than the Fox by nearly $700/set, 2)They have a slightly softer ride on road, and 3)Their adjusters are easier to get to, especially in the rear.
The Fox's have more adjustability, not something I necessarily need but it would be nice. The Fox have aluminum bodies so they would likely hold up better over time to road grime/debris, but seeing how I am in the south winter road salts aren't a factor which is the biggest issue with the King steel bodies. Shafts seem to be wash for a number of reasons so I didn't let that impact my decision all that much.
Both will likely require rebuilds every few years or 40-50K miles so I plan to keep my current Fox 2.0's to swap back on for when the King's need to go in for an overhaul. I have been pleased with the Fox 2.0's but in the last few months the rears have started to get a little rougher in terms of compression. I have had them on the truck for 1.5 years and 25K+ miles now so I am not surprised that they might be beginning to show some performance degradation. That said, they show no signs of leaks or failure.
I have owned both King and Fox 2.0/2.5's in the past so I have very little bias between the two, that said, I hope that I made the right decision in the long run.
