If it was Rawalpindi/isld i would have said bike all the way, but Karachi situation is a lot different.
Reason for bike: No hassle, less maintenance, better economy and amount of time which gets saved.
In university i never used to take car despite father's insistence cuz i knew i would be late for class by almost an hour. Car once it gets stuck in traffic than there is very little you can do.
However if comfort is your priority than definitely car is the obvious choice.