I say go with the Chinatown bus, but be careful what company. I've never had a problem with Fung Wah - it was cleaner and nicer than Greyhound - but the one time I took the Apex line the whole bus smelled like pee.
The other positive aspect of the Chinatown buses is that they're only recently well known, so you're likely to be riding with people who live in Chinatown and students, while every obnoxious, smelly, loud drunk knows about Greyhound and will head straight to Port Authority. I've definitely had more peaceful rides with fellow Chinatown bus riders.
A side note though: be sure to look at a map of the city you're going to before you arrive, as the buses pretty much just drop you on a corner as opposed to a centrally located big bus station.
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