I don't care which kind development you are talking about.City's importance lies in it's economy.Lahore has GDP less than half of Dhaka.Islamabad is a small city of 2 million.Latest data are hard to find for cities concerned here.According to McKinsy2010,GDP-
Dhaka-29 billion
Karachi-28 billion
Lahore-13 billion
https://en.wikipedia.org/wiki/List_of_cities_by_GDP
Chittagong's GDP is not much lower than Lahore.It is the center of trade and industry of BD and have highest per capita income.It's population more than 6 million.
Islamabad is rich but small.It is not very hard to create a planned city of rich for 1 percent of national population.I don't see any credit about having Islamabad being so nice.Pakistan was without any city for capital(Karachi,Lahore are much vulnerable of Indian attack which mostly influenced for going after Islamabad). So a military dictator decided to build a city from scratch just besides of military headquarter.So it is small,planned and beautiful inhabited mostly by elite.
What most important is,Urbanization rate.In 1960 Bangladesh or East Pakistan had only 5 percent population urban while west Pakistan had 22 percent population urban.But in 2015,BD have urban population 34 percent and Pakistan 39 percent.So,Bangladesh started from bottom,now approaching Pakistan level.If BD was East Pakistan I don't think it would have crossed even 10 percent by now.
http://data.worldbank.org/indicator/SP.URB.TOTL.IN.ZS