I fly to NYC a couple times a month, and generally fly into JFK and out of EWR. I mainly do this because of the flight timing. Both terminals are not great, but JFK has the lounge and a bit better experience. EWR is a dump. Precheck times are usually quick at both. I believe most of the flights to Seattle are on 737's, but that might just coincidence because I generally fly the same flight. If you are driving, factor in traffic. I have specifically been caught up in some nasty stuff trying to get to EWR. If you are taking transit, I find both airports easy enough.