The E-2D is an order of magnitude better than the E-2C, which is already by far the most advanced and capable AEW aircraft available to any fleet.
The E-2Ds new AN/APY-9 radar allows for both electronic and mechanically scanned functionality in a more powerful hybrid system that give the operators three functionalities for the systems.
The E-2D radar uses a longer wavelength between 10 and 100 cm generated by frequencies higher than 300MHz to identify aircraft using stealth measures that would normally render them undetectable. The US has been working on and developed, improved, and now has deployed true anti-stealth capabilities to the E-2D, and has the best stealth aircraft to test them against and improve them until they have it tight...which they have done.
The US will build 75 of these aircraft to ensure that they have the test, maintenance, backup, and then the active wings of four aircraft for each of the US Navies ten large aircraft carriers.
Now, the picture shown above is NOT what the Chinese are developing. I am talking about the one that says the US should fear the new Chinese AEW aircraft. That is simply a PS'd E-2C aircraft.
The new aircraft the Chinese are developing are going to definitely be far better than the existing helicopter AEW capabilities they have...but they have a lot to learn and catch up to get their equipment and capabilities up to what the US has been working fifty+ year on developing.
Time will tell how ell they do on their first iteration...but it is something that myself and everyone else who knows very much about US operations has been expecting since it became clear that the PLAN was going to build several carriers beyond the STOBAR carriers they now have two of. I expect they will ultimately develop a force of six carriers altogether, and that over time, they will ultimately make all six of them CATOBAR carriers capable of fixed-wing AEW operation.