Emacs: fido-mode vs icomplete-mode

Difference between fido-mode and icomplete-mode

There are two aspects of difference, submission and match method.

Submit Choice Difference

• icomplete-mode requires you to complete first, then submit your answer. Two distinct steps.
• fido-mode always just select the closest match and submit it.

• The disadvantage of icomplete-mode way is that it's one more keystroke.
• The disadvantage of fido-mode way is that if you are creating a new file (new name), it always submits a existing file name. You have to specifically press some key to tell it you don't want any existing choices. Or answer a prompt that ask you if you want to overwrite. (RISKY)

Matching Method Difference

• icomplete-mode does not use flex match by default. You have to type the starting letter of a name in order to complete.
• fido-mode use flex match (it matches any substring or subset of chars in order.). Usually saves a lot keystrokes.