That's a good question. They are quite similar, but there is a difference explained best in this video
"very" or "tre" are unnecessary.
"the best" is already "the most" good that it can be. If you put "tre" in Esperanto to emphasize this, than you could translate that to "tre" in English, or vice versa, as it is really an English thing to do - emphasizing by adding "very" even though it is unnecessary.