J31 is already at very advance stages of prototype being tested and first flight conduct while Turkey TFX design has yet to finalise, not to mention prototype being build and tested.My friend, J31 and TFX are in the same category. Either J31 or TFX, PAF won't operate two types of 5th gen in the same time. It's a tough choice you have to make, it takes some time. Several points need to be take care of: time of available, sanction free, specification demand, price, production capacity, Maintenance and after service.
I dont think it is a tough call which project shall picked.