They are also easier to install and can be returned if they don't work. Firewall software works by checking data coming in and going out. The programs can be set to block incoming traffic from the Web, such as unwanted intruders. Premium packages include filters that can block pornography or other objectionable material. But the software takes processing power, slowing your connection.
Any lag is barely noticeable except when downloading large files.
Tricky to install. They can be tricky to install because you often have to configure them with proprietary software. Hardware firewalls also can act as routers, directing traffic among various PCs. They can also form the hub of a home network. And they can allow you to set different security levels for individual machines.