Firstly, I'm fully aware that this question gets asked often but it seems like its been a couple of years since the last good roundup of the available distributions.
I'm also aware that the best distribution is often the one that you're most familiar with but for this exercise can we leave that answer out.
We currently support about half a dozen websites spread over two CentOS based physical servers. We're up for renewal and are looking at getting 1 big server running VMWare (vSphere Hypervisor) to manage all current and a handful of planned new sites.
The ideal distribution should be stable and secure, sit happily in a VM envirnoment, and be relatively easy to maintain (in terms of updates and security patches).
Any suggestions, recommendations, or things to avoid?