As chip Zeller says another benefit of migration is the fact that your original vCenter is not disrupted.  you are doubly disadvantaged as your vCenter is still physical, so you do not even have the option of a snapshot to protect provide a roll back.

the only way you can be safe is to have a 100% verified full back up of your environment prior to your disruptive upgrade.

this is about risk management.  present the option to your superiors explain the benefits and also the fact that it actually lowers the associated migration risks inherent with a physical device.