Eversince PAF inducted US fighters in her service they have been quite impressed by the performance. That is why whenever they get their hands on the US fighters they prefer them.
Whenever a new fighter system is to be inducted their are certain things that are kept in mind. Such as ease of maintenance, reliability of the weapon system, expected service life of the system, performance of the system and the capabilities of the system.
When you look at these criteria than you should know that US fighters are better in these qualities than other countries systems. That is why PAF is obsessed with them.
Plus we have more than 60 F-16's in our inventory (32 old one, 14 EDA obtained from USA, 18 new block 50/52). The numbers are expected to increase. Considering our doctrine these numbers are sufficient to make India think before doing any thing stupid.