Personally I always prefer clean building a physical system and then have Ghost Images (or other type images) to restore from to get back to a known good clean working state and then restore User Data. This enables a quicker refresh and can be done in off hours however it's not always practical and each case can be different so different methodologies need to be applied as necessary. While P2V or V2P is doable nonetheless it is not without its issues. This is especially so in cases where some software packages are being activated base on the specific hardware footprint, physical or virtual, and that needs to be taken into account when applicable. In some cases it can be worked around easily and in other cases not so easily. Also depending on OS Manufacture there are certain protocols and or methods that have to be used in order for it to be done in a supported manner.
No offense intended however I'm of the school that if one has to ask then one is probably not the one that should be involved in this aspect of IT Support for a Mission Critical System.