Since you are looking for pro and cons there really isn't a valid list that fits everyone. What one person finds good other would find pointless.
Any case the main reason to keep dual-citizenship.
1. Enjoy the benefits of being a citizen of both countries. (obviously Pakistan has less benefits to offer its citizens but it still has them)
2. Laws for foreign nationals apply. You have to report your stay in Pakistan to the police etc, many are not enforced anyways but who knows countries can become progressive.
3. You lose NICOP as soon as you relinquish your Pakistani citizenship. So that free entry into Pakistan is gone. You would have go apply for a POC card(Also visa free entry for foreign nationals)
4. Certain bank accounts/tax/business accounts are not allowed for foreign nationals.
5. Many government funded schemes are not allowed for foreign nationals. For example, you would not be allowed to partake in the Hajj Scheme that is funded partly by the Pakistan government yearly.
and Cons (not many)
1. Renewal Fees on multiple IDs for both countries.
2. That's about it. The US passport states your country of birth so if you think you can hide your background just because you have a US passport think again.
Oh last thing
NICOP renewal requires you to enter details for US passport that would automatically make you dual-citizen.
