It's not that hard to compare.GaN radar array is certainly bigger on the J-20 than the array that could fit in the F35 but its hard to compare capabilities. Power available and cooling for the radar is possibly better on J-20, F-35 have trouble with that aspect and without real engine upgrades, not sure how they will manage block 4.
Latest J-20 is using GaN-on-SiC TR modules and F-35 is using GaA TR modules. J-20's radar tech is 2 generation ahead. Even with APG-85, J-20's tech will still be one step ahead.