Gentoo is nice, but either you let it get behind or you risk upgrades that will break things. The etc-update system does not adequately discriminate between files that are normally customized for the local installation and files that are not usually changed by end users, leading to a lot of work sorting out configurations every time you update. Gentoo also has wierd, non-standard configuration issues - like the DHCP client over-writing the NTP configuration by default.
I use Gentoo on all my servers (and several workstations) and once the Portage system (and its new /etc/portage configuration) is properly understood and put into place the management of the _cfg files is very logical and effecient.
I agree that Gentoo does do some strange things (like the named package using /etc/bind and then having /etc/init.d/named (versus /etc/init.d/bind which seems more logical to me)) but I think its positives outway its issues. Positivies (in my opinion) like; forums.gentoo.org, very active support mailing list, very active IRC channel, the portage tree is updated daily, package management as a whole works very well, excellent collection of install and configure docs.
I think it becomes the 'do what you know' scenario, my meaning is that if both you and your client are familiar with Redhat - stick with that and use Fedora.
Regards, Steve