If cost is no object, the Acela train. If it is, Megabus and Bolt Bus are fairly reliable both in terms of schedule and wifi. Also check Vamoose Bus, they're operated by DC Trails, a coach company in DC. I'd steer clear of the rest- DC2NY, Chinatown bus, etc.

PS: Amtrak has recently changed their fare structures and cancellation/no-show policies. In the past they were exceedingly generous, not so much anymore.