[Koha] What's best - virtual machine or normal installation?

Hi there, Here, at Arad County Library, we are preparing to implement Koha, but recently the people with whom we work suggested that installing a virtual machine with Koha is a choice we can take into account. I specify that for implementing Koha we have a Fujitsu Siemens Primergy TX200S4, with Quad Core Intel Xeon E5420, 2.5 Ghz, 6GB RAM, mainboard with RAID controller, 2x750 GB HDD, Gigabit Ethernet card and around 200.000 SQL records data base. Is there any serious threat or disadvantage on using a virtual machine? Any ideas, suggestions are welcomed. Thanks! Warm regards? Marius S