ABS (Acrylonitrile-Butadiene-Styrene) and PMMA (Polymethyl Methacrylate) are two materials commonly used to make appearance prototypes. They each have different characteristics, so they are suitable for different types of appearance prototypes. The following are their applicable types and characteristics:

ABS material
Features:
Impact resistance: ABS has excellent impact resistance and is suitable for making frequently used or easily damaged parts.
Processability: Easy to process, can be made by CNC processing, 3D printing and other methods.
Cost-effectiveness: Relatively low material cost, making it suitable for mass production.

Suitable types:
Consumer electronics appearance: such as mobile phone cases, computer cases, etc., because of their durability and good appearance.
Automotive parts: Used for automotive interior decoration or appearance parts because of its good strength and heat resistance.
Home appliances: such as electrical housings, control panels, etc., because of their plasticity and cost-effectiveness.

PMMA material
Features:
Transparency: PMMA has excellent transparency and is suitable for making parts that require light to pass through.
Gloss: The surface is smooth and can provide high gloss, which is suitable for the appearance of high-end products.
Weather resistance: It has strong resistance to UV rays and climate change.

Suitable types:
Optical product appearance: such as lamp housings, display screen protectors, etc., because of their high transparency.
High-end consumer products: such as luxury packaging, display racks and decorative parts, because of their elegant appearance and gloss.
Medical devices: Used for the appearance of medical products that require high clarity and finish.

Summary
ABS is suitable for making durable and cost-effective appearance prototypes, mainly used in industries such as consumer electronics, automobiles and home appliances.
PMMA is suitable for appearance prototypes that require high transparency and gloss, and is often used in optical products and high-end consumer products.
According to specific design needs and functional requirements, choosing the right material will help achieve the best appearance and performance.