For the sake of simplicity, I’d load it on bare metal. Adding virtualization can introduce problems (like memory usage, hard drive issues, and Ethernet port oddness) that can make the system seem unstable.
Having said that, there are advantages in using VMs. You can run a “hot spare” of your VM in some virtualization systems, as well as allowing you to utilize your resources in a manageable way if you are already using virtualization.
Personally (with biases exposed) think that virtualization is an unnecessary level of complication that seldom provides real advantage. Most of the advantages people cite are subjective, unrelated to objective data to the contrary. If, on the other hand, you want to virtualize, knock yourself out.
A better solution (if you are intent on virtualization) would be to go with an installation “in the cloud” (pronounced “on other people hardware”) like Sangoma’s hosted solution. This way, you get the disadvantages of virtualization without the headaches of having control over them.