I am a huge fan of VMWare for server virtualization. They have an excellent management tool, and the platform is rock solid. It’s also get a very light weight OS under it which frees up more resources to the virtual machines than if you run Windows as the base OS (as you do with Virtual Server).
At a prior company we have a large VMWare infrastructure setup with 4 machines for production and about 90 servers running on them. At my current company we are currently only using VMware for development, but will be rolling VMware to host production servers later in the year. We have a single server with another on the way. We have 53 virtual servers running on that one physical piece of equipment.
VMWare offers a free version of VMWare, called [VMWare Server, that isn’t as lightweight (or robust) as VMWare ESX that could get you started in a test environment. Download it and give it a try!
VMware is the market leader at present and on most fronts the forerunner of trends, Virtuozzo is great and has big pluses if you..
A. only use one type of operating system,
B. need big I/O
C. have limited space and no shared storage.
Virtuozzo uses containers to semi snapshot your host, so basically the host system is themain system and your first VM is a container with just the changed files on, so your VM could be only 40 meg, it uses host resources so superfast non hypervisor.
they all have their place and downside is Virtuozzo only allows one type of host but again is host based and good on space, also cheaper budget. free download for this too from the parallels website.
VMware server is good and free and so is Virtuozzo although not free, you do get what you pay for but costs nothing to check out.
I have done installations of both for varying customers and its horses for courses and both work
is only my opinion but hope it helps