How many people here are relying on more than just anecdotes and pictures grabbed off the internet?
Anybody seen both cities? Anybody read more than a single survey of the transportation systems of both cities? Any scientific data or measurable indicators?
While you have specified "roads" as the main thing, it clearly shows the mentality that runs in the minds of urban upper middle class Pakistanis who simply cannot give a damn about a public transportation system. Islamabad's lack of an effective (or an ineffective one) public transportation system reflects the mindset, the ideology, the lack of will and spirit for social welfare and general social uplift among the residents of Islamabad who epitomize the upwardly mobile urban middle class in Pakistan.
I've been to New Delhi more than once and I assure you that while the road infrastructure in old Delhi is indeed incapable of holding much of any traffic and most highways are far worse than ours, the public transportation system is a great blessing for the working class. As most, maybe all members here represent middle and upper middle class, they simple couldn't care less about public transportation which is the main source of transportation for the general public.
Delhi's Bus Rapid Transit System and Delhi Metro both work efficiently, especially comparing to nonexistent public transportation in Islamabad or the existing poor systems in other major cities.
Regularized, administered and managed Public transportation has never existed in Pakistan, for it has never been the state's policy to address it. Local municipalities do not have enough resources to pay off their bills, much less invest in public transport. Provincial governments are deprived of tax revenue, all of which is eaten by the federal government. And the federal government is inefficient, twisted towards working on non general welfare projects and would have filed bankruptcy years ago had it been a corporation. Ineffective and inefficient governance has allowed the exploitation of the general public who are left at the mercy of transpiration mafia who transport 18 people inside a 10 seater van across towns, stopping at every inch of road and causing traffic jams. Buses are overloaded, in dilapidated condition and there exists no municipal control beyond basic price regulation.
I've seen more than half a dozen Indian cities and I can attest to the fact that highways across India are no match for our highway infrastructure. Most major highways across India are undergoing expansion and improvement but Pakistan's highway and inter city infrastructure is in much better condition, is far newer, far wider and overall far better. Intercity transport was painfully slow in India (except the Delhi Gurgaon expressway) compared to Pakistan where you can woof from Peshawar to Lahore in four hours. Our motorway system will be complete till Multan by the end of 2013 and around 2015 it will be Peshawar to Karachi by access controlled highways besides major transportation routes like the old N-5, the newer N-55 and the expansive national highways.
Intracity transport can be problematic and efficient at the same times. Elite urban areas are connected by expansive roads regardless of the fact that they need a 90 feet wide road to carry limited transportation and they have no sidewalks (who walks in an elite neighbourhood, duh !). More populated, denser and older areas are forgotten for nearly every penny spent by the state is deviated toward catering for the elites. Older neighbourhoods in Delhi face nearly the same prospect as far as I saw. Conditions were better in Mumbai and other cities when it came to older neighbourhoods.
Overall, Pakistan has a much better highway infrastructure. India's intracity transportation systems lack much because they have existing and sometimes efficient public transportation systems. They might lack the "width" that appeals to many untrained minds (expanding the road will solve all traffic problems mindset which appeals to most bureaucrats, politicians and appeases the upper middle class as it gives an incentive to buy even more cars to flood the streets).