I'm consistently amazed how different it can be within individual airports
Take JFK - inbound BA T7, if you're in a premium cabin and can overtake the laggards, immigration has never taken me more than 20 minutes as a Brit. On one occasion, I was 5th off a Jumbo (upper deck) and was in a cab 15 minutes later, including picking up a bag! On the way out, premium security line again at T7 is a breeze.
And then you suddenly find yourself having to go through T4....
!