I don't use client, I use server. With a base headless install with broadband via ssh I can have a system up and running in ten minutes. Although I do alot more than just install ZM normally so a full server setup with raid1 mirror for the OS and raid5 for events and database takes between two to three hours tough I making some additional packages that should cut that in half. I have never had a problem with php or sockets on php in CentOS But I have now been doing this and making packages for ~6 years as well as Ross. Same goes for Fedora as it was what I really learned on 7 years back .
The last 4 years I've been running xen, shame that xen is being dropped by Redhat because it will not be included in the Kernel so I am hoping that KVM will be as good as running the Xen micro kernel, but alas I have already pretty much committed everything to the xen platform so kvm will need to likely really exceed xen performance and features before it's worth me putting that much work into it. Redhat really missed the boat on that one.
As far as the different ZM distro's goes, it really comes down to how well it is supported and how stable it is. The latest and greatest is fun until you run into a bug that brings everything to a halt, then you either have to pull your hair out going through the forum if you are not sure what is wrong, or pay to have someone support you to get it fixed right quick. Then there is the issue of updatability and faith that your not going to lose your data doing so, and how well it is maintained and those doing so are going to always be accessible when things go wrong.
As far as the Linux distros goes, my laptop or I guess I should say netbook, my daily driver has Ubuntu. Now Ubuntu is awesome, it's easy to setup and have all the bells and whistles. Why do I not create or use packages for Ubuntu? Because of ffmpeg and we need to have the latest SVN release and also Peter already does an awesome job of it him self. Ubuntu has ffmpeg already packaged but like most all distros they are usually at least a few months behind, then add to that the other packages you might desire to install that depend on that version of ffmpeg that the distro has packaged and could end up with a conflict as it's available in their repo. Since Red Hat is in the states, they don't want to deal with licensing issues or certain patent holders, so they do not package it as someone might want some money for every installation out there. So when you get RH, the predefined repo has no ffmpeg. That's great for us because we don't have to be too concerned about running into dependency conflicts, the down side is I to live in the states

but from a support stand point, I have less to worry about someone dong something that creates that conflict as it takes a bit more effort. That's why I stick with RH at least for now.