I hear people saying "this clone should just be an alt-costume!" Some people believe you're saving time or memory...all you're saving is one little character select square...but doesn't creating a new model for the character take the same amount of work and effort to create an alt costume... An alt costume is like a clone...only worse.
Then people say "hey, they could slightly tweak the moves of the alt costumes!". Now that is COMPLETELY equal to a clone...
Clone- a character model with the same moveset as another player, but with different stats.
Why do some people think they are saving time or memory? If it's a simple color-swap...well that's nothing. But if you want Young Link to be an alt of Link, or Pichu to be an alt of Pikachu, or Dr. Mario to be an alt of Mario...well in that case you're getting something worse than a clone. You get character model with EXACTLY the same moveset.
In conclusion, I believe clones > alt costumes