The PRR named every train on the Corridor, and I never heard anyone speak of taking the Legislator, or the Mount Vernon, or the Judiciary--it was always the 8:30, or the 9:30, or the 10:30. The few exceptions were the Congressional (which deserved a name, considering it carried an all-drawing room parlor car in addition to five or six others), and often the Boston trains. In any case, the term Congressional had a certain cachet at the time, which I fear has been lost in more recent years ...
Having ridden in the Alexander Hamilton (former PRR Congressional parlor car) while it was in service on Maine Eastern and Acela FirstClass (more than once) I would offer this perspective ...
Acela was by far the better experience of the two. Although I completely acknowledge that the service offerred by Maine Eastern was not Pullman in the 50s I can at least compare the accomodations.
Acela FirstClass was just as comfortable (if not more so) and in many ways a better experience. The sight lines throughout the FirstClass cabin make for better viewing than the Alexander Hamilton which had partitions between sections of the car. The observation end was fun but ultimately a seat at the window in FirstClass is at least as good if not better (it's also bigger).