The nicer bus services are totally fine, and are actually easier from the suburbs than schlepping all the way to Union Station (and then back) for Amtrak, which can add an hour or more. I would not take Greyhound.
I travel between Bethesda and NYC quite often and have taken Tripper and Vamoose. Both I think stop in VA as well. I’ve also heard Best Bus is decent and stops in Vienna, but have not taken it personally. I do agree that travel time will be around 4.5 hours and the earliest departures are around 8am, latest around 5pm, so you’re not going to get much time in NYC if you’re doing a day trip on the bus. Amtrak might be better since you can leave early and get back late.