If you need to choose between using integrated functionality in a network device versus using a specialized function appliance, first and foremost you must make your decision based on:
A.
The capacity and functionality of the appliance.
B.
The integration advantage of the device.
C.
Ease of implementation, use and the maintenance of the system.
D.
Limiting the complexity of the design.
Explanation:
The integrated functionality is often attractive because you can implement it on existing equipment, or because the features can interoperate with the rest of the device to provide a better functional solution. Appliances are often used when the depth of functionality required is very advanced or when performance needs require using specialized hardware. Make your decisions based on the capacity and functionality of the appliance versus the integration advantage of the device.
REF; Safe white papers; 4
SAFE: Extending the Security Blueprint to Small, Midsize, and Remote-User Networks