I have discovered that it is cheaper for me to drive if I have 3 or more of us going. If it's just 2 (or I don't have a parking option - we usually stay at a hotel with parking) then it's comparable to what gas and tolls total. If it's just me then I take the bus.

I just took my mom to NYC for Mother's Day. We took a bus - specifically the Vamoose Gold bus which is a bit expensive compared to the other bus options but still cheaper than the train. I wanted the train at first but cost was crazy. It was a very comfortable 4 hour trip - direct between Bethesda and Penn Station. I would totally do it again.