SAFE Blueprints says to this topic:
At many points in the network design process, you need to choose between using integrated functionality in a network device versus using a specialized functional appliance. 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. For example, sometimes you can choose an integrated higher-capacity Cisco IOS® router with IOS firewall software as opposed to a smaller IOS router with a separate firewall. Throughout this architecture, both types of systems are used. When the design requirements did not dictate a specific choice, the design opted to go with integrated functionality in order to reduce the overall cost of the solution.
Link:
http://www.cisco.com/en/US/netsol/ns340/ns394/ns171/ns128/networking_solutions_white_paper09186a008009c8a0.shtml
1.) I think the question is about if you need special devices as Serial and ADSL interfaces for Firewalling as it is supported by the IOS Firewall. The PIX is more limitated in which devices it support, usually Ethernet, Fastethernet and Gigabit Ethernet interfaces.
2.) Both of them are Statefull Firewalls.
3.) PIX is a high performance applicance that has limited QOS and Routing features.
sincerely
Patrick
