Generally speaking, here's a rundown of each. Pubs are primarily blue-collar, the place where rugby fans like to call home. Yet you are as likely to rub shoulders with well-dressed businessmen. Pubs are the London's original drinking establishments, and some of them have a history as rich as the city itself.
Bars are upscale establishments with people wearing the latest style clothes.
Black is always a safe bet here. Drink prices are hefty and the crowd is generally young and impressive. Don't worry about passing any inspection of a doorman to gain entry at the latter. There is a third version, kind of an upscale cousin of the mega club, and that's the private club. These are pretty much for members and celebrities only.