Kayani served as DG ISI. He knew the inner workings of Pakistan not visible to others. He carried on this perception of Pakistan under constant existential threat into his COAS role. He therefore probably believed in good taliban vs bad taliban, since he probably dealt with them. He knew how much control he had over who. Who was out of control and who needed to be taken care of. Whether they had any use for Pakistan or not. He had all under a magnifying glass.

Raheel Sharif is a pure soldier. He served as IG training and evaluation. Had a major role in formulating doctrines and training to tackle terrorism. In this role he always viewed the taliban as terrorists because he was constantly devising plans against them. They were always a threat to him. He didn't know the inner workings of ISI. He carried over this perception into COAS and you can see it in his actions.

Conclusion: Both are patriots and did what they thought was best for the country.