> Keep in mind airline miles. I take the shuttle out of LGA to D.C. over the Amtrak.

Anecdotally: people where I work do a lot of traveling between our NYC and DC offices. Only one person flies rather than taking Amtrak...

I did a bunch of trips recently. Flying is usually faster and cheaper, but more likely to go awry. Taxis to airports can vary widely in speed and cost. Flights can be delayed, security lines, etc.

Train is easy, consistent and comfortable. Always power, Wi-Fi and cell signal too.

> Train is easy, consistent and comfortable

Fair enough. I'm an infrequent NYC-DC commuter. And my preferred mode to JFK from the city is via the LIRR, a rail route. It takes longer, most of the time, but less time on average. Most importantly: it's consistent.

I optimize miles too but, for short distances, it's mostly not worth it. For Boston to NY I essentially always take the train which is more comfortable if not necessarily faster. And Amtrak points are probably actually more useful for me in general than airline points. I'd get 500 points on United and use of the lounge but, really, that's not worth a whole lot. Amtrak is already basically as comfortable as an airline upgrade--which is hard to get on a weekday peak travel slot.

Of course it's all just going to depend on your situation:

* How often you travel

* How much you will be able to take advantage of perks

* How close you are to various terminals/airports

* How far you regularly need to go

* How you like to travel (fast & cramped, slow & spacious)

etc.