My definition of each is:
Caricature=Distortion and exaggeration of a subject's distinctive features
Abstraction=Simplification down to a subject's essential features, eliminating unnecessary information
Abstraction is one expression of a design principle called Signal-to-Noise Ratio, which states that the Signal is any information that is important for the viewer, while Noise is unimportant information which necessarily interferes with the signal.
The key in any good design is to identify how much of the detail is actually signal, and downplay/subdue/eliminate everything else. In other words, not all detail is noise---sometimes it's part of the signal. The best way to judge whether a detail is signal or noise is:
- Does it say something important about the character?
- Does it enhance the overall style of the piece/property? (ie. Does it say something about the world?)
- Does it significantly increase the character's appeal to my intended audience?
- Will the audience be able to see/appreciate the detail or is it just adding clutter to the scene?
If the answer is no to all four, tone it down or cut it out!