I have used light rail transit in NYC, Washington DC, Chicago, San Francisco (cable cars and BART,) San Diego and London, so my experience is pretty limited.
I like New York's because the local and express lines allow you to get around quickly and efficiently and, because of the local local lines, you don't have to walk too far to get to a station. I have to admit that it's been years since I've been there and my experience is mainly limited to Manhattan, so maybe it's different nowadays.
London's is great because you can get around to the touristy places easily and it's relatively inexpensive. And it's pretty extensive.
The others are good and a better option than driving.
I like New York's because the local and express lines allow you to get around quickly and efficiently and, because of the local local lines, you don't have to walk too far to get to a station. I have to admit that it's been years since I've been there and my experience is mainly limited to Manhattan, so maybe it's different nowadays.
London's is great because you can get around to the touristy places easily and it's relatively inexpensive. And it's pretty extensive.
The others are good and a better option than driving.