Flying from USA via Dulles Washington DC vs Kennedy New York
 

I recommend flying through Dulles as the lines & customs coming back are MUCH easier/shorter! The customs in New York took us 2 hours once vs 30 minutes in DC

Look, you know as well as we do that the amount of time through Customs/Immigration depends on the number of same-time flight arrivals and the number of agents on duty and the number of people trying to clear.

I am really happy you've had faster experiences at IAD but that doesn't mean it is going to happen every time.

I am a US citizen and I travel internationally at least twice a year. I never remember waiting longer than 45 minutes to pass through JFK immigration and a wait of even that long is rare.

Most returning travelers do not even go through customs and if they have to have their bags examined, there is never as far as I know, a wait of more than a few minutes.

Having said all that, I know that non residents often have terribly long queues.

And I rarely travel in summer, so perhaps the situation is different in peak travel season.

As others, depends on time of day of arrival and number of other int'l flights at the same time. There have been times when there is no queue at all, others a few minutes longer. Haven't ever waited more than 30/min if that, but it's often the baggage that can take time. I personally find IAD a bit drab, dark and unappealing... as if travel anywhere can be considered otherwise! NOT!

And I sure wouldn't fly out of IAD when most every air carrier flies out of JFK, at least wherever I've had to travel.

I live not too far from IAD but have flown from JFK when that flight was direct rather than from IAD where a change of flights was required. I have learned from bitter experience that there is no such thing as a truly safe connection time.

There is no way to tell how things will be on any given day or time, but during our previous years overseas, we always preferred flying in/out thru IAD. We still use IAD to get to Pennsylvania from Houston/New Orleans, as we are just very comfortable with that airport.