For casual spoken English in Canada, they are equivalent. For an English exam, "the train leaves at 8 a.m." is preferred. More information: https://www.ef.com/ca/english-resources/english-grammar/future/ [excerpt] Time-tabled events: The plane takes off at 3 a.m. Also, see English Grammar in Use 5th Edition by Murphy, unit 19.

Hey Alejandro, Both are grammatically correct. However, there's more to know. "The train leaves at 8 a.m." can be used to talk about the current train situation (the near future) or the train schedule in general. "The train is leaving at 8 a.m." can only be used for the near future and not the general sense. Hope that helps! -Chase

Both are grammatically correct, but the first one sounds more natural.