Only a small note to let you know that Virtualmin (from version 3.54) can be used for serious work when importing websites from Plesk backups: I tried the previous version with some web sites but it was too buggy, so I decided to help authors in debugging and testing it; I think that now Virtualmin can import the backups in a rather complete way.

BTW, Plesk is a good product, full of features, but I prefer Webmin/Virtualmin because they let me have full control of the server, instead of the way of Plesk that is too automatic in my opinion and offers less choices, impositions that I feel too strong (one for all: Plesk comes and works only with QMail).