I don't think we can conclude KJ-500/J-20 is better than E-3/F-35. USAF gets uncomfortable anytime they think they might not have an advantage. And in this case, I think they have concluded E-3C is not helping them against J-20, but KJ-500 is tangibly helping PLAAF find F-35. They believe E-7 will help them against J-20. There are many other aerial assets like other fighter jets and drones that can affect things also.It could be that all the E-7/F-35 combo provides the USAF is parity. It could even be that the E-7/F-35 combo is still worse than the KJ-500/J-20. All we can conclude is that it's better than E-3/F-35.
I think until we get serial numbers, J-20 sightings could be explained by any number of things. It's reasonable to assume that more units will get J-20s this year. Let's wait for photos.Sorry for the confusion, but if they were seen there, then it does not mean they must be based there and as such could well be from the 9th AB?
My point is, there seems to be some sort of hype recently and even if - as @Bltizo noted - it could be that several units are gaining just a few J-20s instead of a full dadui and will be later filled up, there are at least by my feeling too many units under discussion right now.
As such it could also be an explanation that they are not always from a new unit but from a visit, a detachment of an exercise, ... whatever.