Is it the comparison just between two engine and single engine?
What theory or study says twin engine aircraft is superior to single engine?
It depends on what role they were designed. A single engine aircraft like JF-17 is very effective in ground support and point interception. PAF JF-17 also has BVR capability. Its RCS definitely smaller than any Indian aircraft gives it higher advantage.
Just because Indians have MiG-29 doesn't mean its superior. Its a high maintenance aircraft.
As a reminder, 1971 war, a much more modern IAF MiG-21F was downed by an old PAF F-86 Sabre Mk.6.
No matter how advanced your plane is, its the pilot and his capability that makes it an effective fighting machine.