Before anyone calls me an ISPR bot, I first learnt the following from an Indian author.
In Kahsmir, Pakistan lost Turtuk, India lost Chamb (which is a strategically important town used as a launching pad for offensives into Akhnoor/Jammu region)
On the international (India-Pak) border in 1971 there is a more interesting story.
India captured much more territory than Pakistan. However, it was almost exclusively barren desert in Sindh which had little to no economic or political significance.
On the other hand, this was offset by the Pakistan Army capturing smaller quantities but far more economically important areas in Punjab.
Although the large quantity of territory India captured was a great talking point for domestic propaganda and jibes at the Pakistan Army, both countries' leaders were well aware of the ground realities.
Both countries tried to retake lost territory post ceasefire. Indians recaptured a sand dune occupied by Pakistan and lost tens of Para SF soldiers.
Pakistan would also launch multiple post ceasefire offensives of varying magnitudes to capture tracts of lost territory in Kashmir, including in Turtuk, inflicting heavy losses on retreating Indian forces. Otherwise they would silently salami slice tracts of Indian held territory.
Hence, at Simla, India returned thousands of square miles of Pakistani territory in exchange for around a hundred square miles of Indian territory. India would also give up Chamb while retaining Turtuk and the ground positions at the time of the Simla agreement would become the LoC. Siachen was left unmarked.