Bingo. You got it. Ground Clearance. Pictures of the J-10 show it carrying large anti-radiation missiles, it could potentially carry the CX-1 anti-ship missile.The Mirages are indispensable for PAF at the moment because of their strike potential via H2/4 missiles. I doubt JF-17 will have the ground clearance to carry these as havnt seen specs stating it can carry those. Can any member check if J-10C has the required ground clearance for the H2/4. If yes then the J-10C is a perfect Mirage replacement, because don't expect Azm/J-31 to be able to carry H2/4 as well.
For the AA role JF-17 Block-3 offers similar capabilities but the H-2/4 capability is something which really gave PAF a edge over India in strike capability.
Even if PAF has ordered any J-10C to counter Rafael acquisition we will only find out when they will be delivered.
Inducting the J-10 can fly further, carry more, and linger longer over an area. Its large radome allows a more advanced radar, and its shape indicates it will be more maneuverable. While the JF-17 Block III can be made to have modern electronics and weapons, it is not large enough to carry certain missiles such as the large anti-shipping missiles, and long range air to ground cruise missiles like Babur.
PAF also needs to speed up replacing older aircraft. The mirages are antiquated, and if we are to field a decent platform for strikes, we need to start now, so our pilots can get the necessary training time in.
Finally, the J-10 can be a replacement for the F-16, as the MLU aircraft will need to be retired in 8-10 years, the political risk of spares being cutoff it any hostilities flare up similar to post 1998 Tests / 1999 Kargil, and the expense of inducting the twin engine stealth J-31 will make it miss match for countering the bulk of even a revamped IAF fleet.
We have 139 F-7P/PG, 172 Mirages, and eventually 59 F-16A/B MLU that need replacing within the next 10 years, If we commit to two squadrons now at 36 J-10CE, we can see how the threat build up develops and buy a further 36 J-10CE thereafter accordingly.
We have 101 JF-17s and Plan to build 50 more Block III JF-17s. That leaves 160 more planes that need to be replaced if you exclude the F-16s. Work on Project AZM will hopefully yield a Decent Stealth Fighter or Stealth UCAV, and hopefully the JF-17 Block I and II can be rebuilt to Block III standard to keep up within our means.
BTW, With the Rafale induction by the IAF, and offering like the F-21 (F-16 Block 70), what enhancements does the J-10CE need? One Enchancement is the need for an Active Decoy on a tether.