In general, the construction quality on F-35 looks better to me. It looks to me to have better stealth alignment from the back and the side. J-20 to me has some gaps at the back that looks like potentially could give higher returns. It also has more stuff going on with different surfaces that would be harder to manage radar returns from side angles. J-20 looks pretty good to me from frontal point of view. I'm also of the camp that canards are probably a negative for radar signature also.
To me, a production version of FC-31 could be better than J-20, but we need to see more. Until we see a more production worthy version, it's hard to say how good it will be. So far, my biggest concern for it is from the rear end. Now, one big advantage J-20 has would be the more powerful EW suite, which could just make opposing radar harder to track it.
i just see a lot of side radar of x/l-band everywhere. the MAWs are not the same as EODAS you would find on J-20 or future J-35 imo. All these side radar to me will just light up the passive receivers and are gimmicks. When you install that many strips of l-band radar, are they going to all have LPI property or are they more likely to operate on narrow band and get picked up?
As I said above, I see FC-31 has potential to be more stealth than J-20 just from a layout point of view. To me, it never got the necessary funding until now. And, it's not primarily an export plane. It will be inducted into PLAAF in large numbers. As such, I see the J-35 prototype to be closer to what the land version will look like than FC-31V2. I would expect it to have EOTS and a more modern version of EODAS.
Sure, most military purchases are very political. That's why having a product that can appeal to countries with bottomless pocket also allows them to advance political agendas with those countries. With Pakistan's help, China could really approach all these Middle Eastern countries and offer them something that can at least compete with F-35s. It would have similar T/W ratio, possibly shorter range and similar generation of avionics (as the more recent F-35 blocks) and be competitive in stealth. It would take much for these countries to look at FC-31/J-35 and see a stealth aircraft.
As for your other point, I think we cannot compare J-20's progress to su-57 or any other aircraft. J-20 was a huge program success by any measure. It started mass production before anyone thought it would. We will have to see if J-35 can match that. It's a huge leap for China's aerospace industry to be able to mass produce a 5th generation aircraft and still keep up the production quality. That took a lot of investment in production technology and industrial strength to do so. If J-10 was China's Apollo project, J-20 was Apollo 2. F-22 was never produced at the rate that J-20 is produced at. Only F-35 is produced at a higher rate, which speaks for the strength of American aerospace industry. I'd be very impressed to see FC-31/J-35 reach manufacturing stage and mass produced at 30 to 40 aircraft a year. Again, ramping up production of a 5th generation aircraft requiring very precise manufacturing is really hard.
I'm sure Iran would want it, but what could they offer in return? More importantly, would that cause China to lose possible sales with Saudi Arabia, UAE, Turkey, Qatar, Egypt, Oman and other countries in the area.
