Washington DC and New York airports choice (USA)

I'm shortly going from Vancouver in Canada to Washington DC in the
States, then Washington DC to New York, then finally to Switzerland
from New York.

Both aboventioned US cities have two airports each, and I'm not sure
which ones are best for arriving/departing from....

Washington DC: Washington Dulles
Washington Reagan

New York : John F. Kennedy
La Guardia

I plan to stay in a reasonably priced backpacker hostel both places,
in central locations, so I'd prefer the airports closest to that, and
with public transport access throughtout the day.
Suggestions?


Hallvard