I've read in discussion arguing between which is more important in character design: appeal or uniqueness.
Appeal
The first option is appeal; is it more important that a character is more pleasing to look at than it is different from the rest of the cast?
What it is?
It's... difficult to explain in words. It's basically "anything a person likes to see". This does NOT default to 'cute' or 'cool'; there are various types of spectrum and appeals:
- quality of charm
- pleasing design
- simplicity
- magnetic
- communicative
A user is drawn to the figure that has appeal, and its gaze is held while they appreciate what they are seeing.
Shock value, like ugly or repulsiveness, can draw in, but they cannot build nor identify a character to allow the user to further appreciate.
Uniqueness
Uniqueness is individuality, the difference between a main character and its species, friend group, team, camaraderie, etc.
Is uniqueness more important?
Uniqueness is important when building a cast, not when fleshing one character or aesthetic. An appealing theme can be generated from a unique cast. However, a unique yet unappealing cast is about as wasteful as one unappealing character.
Cookie-cutter phenomenon
What tends to happen when an appealing character is reiterated with single or minor changes, such as clothing, skin or hair color, the initial appeal of that strong character design tends to wash out from repetition. Dramatically, the hard work in making that one appealing character is made worthless when simply reapplied to another.
In a way, uniqueness falls under appeal.
Of course, two characters with several of these properties altered will certainly , but if the overall frame of both of these characters are still too similar if not identical, then the phenomenon has still not been addressed.