> Paris is a marvel for its density and well-planned routes. But some of the lines are more like underground light rail compared to e.g. the Lexington line, which on its own carries like 1/3 of the passengers of Paris or London.

So maybe that indicates that more, smaller lines are the way to go? Passengers don't care how many passengers each line carries, they care about being able to make their journeys.

> The London Tube trains I've been on felt like a subway for midgets compared to the 10-foot wide BMT trains.

You get used to it. They're small but again that's not inherently a problem. (Being overcrowded is a problem - I don't know how NY or DC compare on this front)

> They stop running at night.

As of a few months ago there's now limited service on friday/saturday nights. But yeah, all-night running is absolutely something NY has over other subways. How much of a priority that should be is a judgement call of course - it's achieved by four-tracking the lines, so if you didn't need all-night running you could have ~twice as many lines (build the same number of tunnels, but spread them across the city better) for the same price.

> One of the only times I've missed a flight was due to a London Tube delay.

Anecdote != data - how do the statistics on late running compare?