I have had the privilege if riding in trucks with all 3 brand 3.0" shocks,
they all ride better than stock, but as it was said, it comes down to riding conditions, driving style, terrain, ect. I think that the shock upgrade is one of the best you can spend your $$ on, in conjunction with a uniball UCA. It is a upgrade you will feel right out of the drive way. We sell king and Icon so I have talked with both and know that they have spent alot of time doing R&D on their products, I'm sure that Fox has as well I just have not spoken directly about it.
All 3 companies have a very high level of fit and finish on their products, and all 3 have great customer support as well as a large network of dealers to assist you.
do your homework, pick up the phone and actually talk to educated sales people about it and ask the questions, not just sift the forum to educate yourself.
I know we are as I'm sure all of the vendors are here to help, it's a big investment.