In the last couple of months I have taken early morning and lunch time departures on AA out of T3 and each time minimal wait for Immigration and security in the regular line. Took 20-30mins max in my case.
I took a flight to DCA with Air Canada in January using T1 pre-clearance, and that was a NIGHTMARE. It was an early morning departure, and because T1 has way more US bound flights, the lines were long, it took over an hour to be processed.
I think it depends on the departure time, but in general T3 is normally very quick as the number of US departures is smaller + most planes are just regional jets.