The K-8 is not on the same class as the L-159. The K-8 was built as an intermediate jet trainer and later modified for light-attack. The L-159 is an advanced jet trainer/light attack aircraft. The avionics are newer, the engine is more powerful, the cockpit is better.....overall a bigger aircraft. Had the K-8 been modified by PAC, it would've been a serious contender to fill in the coming-soon gap for OCU but R&D is being pushed further more for a new JF-17 variant, a new fifth generation fighter (impressive with the lack of experience on 4th generation eh ??) and supposedly commercial aircraft. I personally prefer the T-50A, the T-50A can be a great addition in my opinion to PAF for OCU (commonality of spare parts with existing F-16s would help too), then again it all depends on US-Pakistan relations. Cheers !!!