Husain thinks that Pak has gained economically by partition - it's true enough. Not due to the 'Hindu Rate of Growth' but due to the all knowing, ever-loving Chacha Nehru. Even here I am not so sure - the richest areas in Pak are in Punjab and Sindh - which would have continued to be rich in undivided India.
The bigger loss is that out of it's Islamic yearning the Pakistanis have disinherited themselves from modern learning that the British presence allowed us to achieve (yeah they impoverished us - but they were not as bad as the Mughals). This is a long term loss of competitive advantage. In the long term a free market of ideas and goods - makes for an economically richer, culturally productive and technologically advanced society.
However, it is an interesting game. I think overall the partition was good as it allowed Hindus to at last have a geographical area where they were a big majority. Otherwise the religious question would have hobbled us forever. It was bad because the Muslims that most fervently wanted Pakistan - those in UP, Bihar & the Nizam's kingdom - have remained. And so we continue to be hobbled ...