Both are still basic packet filters however and do not allow for advanced features such as stateful inspection or some types of proxying connections. Your first choice to make is whether to go with default deny or default allow policies, followed by which services and hosts you wish to allow and block. I typically use a policy of default denial as it can accommodate mistakes and changes more safely then a policy that defaults to allowing data through. If you have chosen a policy of default allowal, anyone on the Internet can access the ftp server, and silly you, you installed an old version which allowed someone to compromise the machine. If on the other hand you go with a policy of default denial, they would not have access to the ftp server, and neither would your users, but you would find out quite quickly.
Annoyed users are much easier to appease then fixing a network that has been compromised.
I have decided to not cover specific firewalling rules in this section, for each network service I will provide examples, as to properly firewall a protocol you need to understand how it behaves. You can insert, append and delete rules, set default policies, and list all the rules. Other then that it is very similar to ipchains, with some minor variations. You can also use this in conjunction with quality of service routing, the example given in ipfwadm's documentation is that of prioritizing traffic going over a PPP link, you can give telnet traffic a much higher priority then say ftp, reducing latency problems caused by a saturated link. This script needs to be edited if you plan to use it.