In January I asked for the same advice for doing WAS-EWR-MEX vs. WAS-IAH-MEX and was told use IAH, avoid EWR at all costs. Did I listen? no, I chased the extra mileage and the greater likelihood of a longer flight in F. ATC delays made us late into EWR and I missed the MEX flight by about 1 hour; finally reaching my destination 18 hours after I wanted to.

Is the reason for the different advice because mine was for afternoon flights whereas the OP is asking about early AM flights?