I wont discus , the quality of using a linux computer for a firewall (probably a good idea), but do you really know, a guy asking for the best firewall knows something about linux .
And even if he knows something about linux doesn\'t mean he necessary knows how to setup a linux computer as a firewall .Take it from me there\'s never a best , there\'s always better , and all this depends on the client ,on what he wants , can afford , or can handle . At least in my humble opinion .