When choosing ABS plastic and aluminum alloy as structural prototype materials, you need to consider their respective characteristics and applicable scenarios. Here is a comparison between the two:

ABS plastic
Advantages:
Lightweight: ABS is relatively light and easy to carry and handle.
Processability: Easy to manufacture through 3D printing or CNC processing, suitable for rapid prototyping.
Cost-effectiveness: The material cost is relatively low, suitable for mass production.
Impact toughness: ABS has good impact resistance and is suitable for structural prototypes that require a certain degree of durability.
Disadvantages:
Strength limitation: Compared with aluminum alloy, ABS has lower strength and heat resistance, and is not suitable for high loads or high temperature environments.

Aluminum alloy
Advantages:
High strength: Aluminum alloy has higher strength and is suitable for larger loads and pressures.
Heat resistance: Compared with ABS, aluminum alloy can maintain performance at higher temperatures.
Fine processing: High precision and complex shapes can be achieved through CNC processing, suitable for prototypes that require tight tolerances.
Corrosion resistance: Aluminum alloy has good corrosion resistance and is suitable for a variety of environments.
Disadvantages:
Higher cost: Aluminum alloy has high material and processing costs, especially when producing in small batches.
Heavy weight: Compared with ABS, aluminum alloy is heavier and may be inconvenient in some applications.

Summary of applicable scenarios
Choose ABS plastic: If the structural prototype is mainly used for appearance verification, functional testing and does not withstand high loads or high temperature environments, ABS plastic is a suitable choice.
Choose aluminum alloy: If the prototype needs to withstand high loads, be used in high temperature environments, or require high strength and durability, aluminum alloy will be more suitable.

Conclusion
The final choice should be based on specific application needs, budget and performance requirements. If there are high requirements for strength and heat resistance, aluminum alloy is more suitable; if cost, light weight and processing convenience are concerned, ABS plastic is a better choice.