U.S. always has better engine, better reliability, efficiency, as well as trust. During Cold War, Soviet never had any better engine neither. I think China at least need 10-20 years to catch up.
China J-20 is specially designed for West Pacific theater:
- First island chain depth is 500km (Okinawa, Japan), 1200 km (Yokosuka, Japan), and 2000 km (Singapore).
- Width is around 5000 km, from north (Yokosuka, Japan) to Singapore.
West pacific theater is much larger both in width and depth than Central Europe theater during the Cold War:
- Width is 700 km from Baltic to the Adriatic Sea.
- Depth is zero, the border is frontline.
- There are tens of military airfields and hundreds of civilian airports in West Europe available for F-22.
- F-22 is designed for Central Europe theater during Cold War, short leg is no problem.
- J-20 is designed for West Pacific theater, long leg is a priority.
Distance from China to Guam is 3000km, the military exercise conducted by PLAAF & PLAN in South China Sea clearly tells the drills of assaulting Guam with fighters, bombers, ships followed by seizing the island with paratroopers & beach landing. Yes, the J-20 is made for long range sorties with the long wide fuselage for optimum higher cruising speed and range.
There are alot of articles stating that the USA 6th Gen will be as large as a F-111 jet and has been designed for the Pacific theatre specifically.
So - the J20 will ultimately have to face the USA 6th Gen until it can get its 6th Gen in place.
Could be larger than F-111 looking at the volume and requirement to operate at stratosphere altitude making it almost a space fighter powered by ramjet or scramjet or something more sci-fi. It's more of intercontinental fighter bomber. Its armament depends whether US could perfect the laser cannon, if no then it would carry hypersonic missiles & usual standoff missiles.