When you are creating a firewall filter rule on a router, the amount of options you have is incredible. For example, most other firewalls or routers will not give you the option to select a connection state, a packet size, specify the packet content etc.
You can use the routers in transparent mode, when your router is placed in front of a customer firewall or customer router, allowing only the allocated public IP address to communicate with the Internet and allowing you to allocate a certain bandwidth or speed.
The lowest end model routers have the same operating system, features as the more expensive ones making simple for us to test configuration on cheap equipment before commit to buy the more expensive one. The licensing model is very simple as well and easy to understand.
The cheapest routers also come with one SFP port, which is great as it is allowing us to connect fiber straight into it. No extra PoE injectors and converter are needed, reducing the number of points of failure.