Who wins?
"night!" vs "bye!!"
"night!" wins 54% to 46%. 44 more put them in the same row. From Ways to Say Goodbye in a Text Tier List. Pick a side.
matt.m17 on "night!": the exclamation point is doing all the work
ThePenguin on "bye!!": two exclamation marks means they like you
Ways to Say Goodbye in a Text Tier List: the full ranking