Just to add: Not only is metro north cheaper, there is way more flexibility in schedule. More trains per hour, and you don’t have to buy the ticket in advance, so you are not locked into a certain schedule. If you aren’t ready to leave at 7pm, just take the 8pm instead, etc.

I usually drive to Milford and take the train from there (there is free parking on the weekends). I don’t know anything about the Hartford line because I’m not up there, but it sounds like a reasonable option. I only take Amtrak when I am going to the airport (Newark or Boston)- for that, it is a lot easier than navigating the commuter trains.