I live halfway between New York City and Montreal, and the most convenient way for us to get into the City is Amtrak. I used it regularly before I retired (I was in the City at least once a week during my last year), and wife and I continue to use it for the occasional 'day trip'. It's much quicker than air travel (no security hassle, and it takes you directly to the center of the City rather than an airport an hour away), and it's less expensive. And there's something comforting about riding the train. On the other hand, a friend once said that the one thing that Amtrak has been able to accomplish with total success is to demonstrate that the railroads could lower their standard of service to match the airlines.
The issue with trains is that there is usually a wait between the time the inbound train arrives, and the outbound train departs. And since there is no seating at the track itself, you have to go do a waiting room. There is no
'arrival' and 'departure' area per se.
And to complicate matters, it's generally not know for sure what track a train will depart on until just before departure - that's because trains are assigned to tracks as they are available when the train arrives in the station. It is true that there can be a 'usual' track for a specific train, but there's no guarantee that the desired train will actually be on that track on a given day.
My recollection is that at Union Station, the track level is only very slightly lower in elevation than the waiting room, and that there is a ramp that you must take down to the track. That's unlike Penn Station in NY where the waiting room is probably 50' higher in elevation than the track, and you have to take either an elevator or escalator to move from one to the other.