Wifi usually blows
I take the Northeast regional from RI to Philly once every other month or so, usually the wifi is painfully slow, to the point it's unusable and I'm just using LTE which is a crapload faster. Some trips it works but for the most part there are too many people using it, it'll take 30+ seconds just to check email on an iPhone. Plus streaming radio(Pandora, etc) is blocked so it's not good for much more than checking email, facebook, etc. It continues to work in the train tunnels in and out of Manhatten though, when regular cell service is obviously non-existant, until you get to the tracks for Penn station where they have cell service repeaters serving the tracks underground.