The point of migrating from Windows to Linux is, for most people, twofold: to reduce cost of software (not a huge issue for an average lawyer though) and to provide a more stable and secure system and in my opinion, an easier and more productive work environment.
If a person is using Office in a virtual machine, that person will likely end up using the virtual machine to also browse the web and work with email. E.g. just think of the steps needed to email a document in such a setup. Person would need to save it to a shared folder, then switch back to the host machine and send it from there. Or say that you want to use a desktop search tool, such as Beagle, to access your documents...
If one's daily routine is inside a guest, then one is going to feel all the downsides of the guest operating system.
Snapshots are great, but in a real world scenario, a lawyer wants to have all her documents backed up and a spare machine in case something is wrong with the main one (be it malware or failed power supply). Virtualization can only save you if the hardware is still functioning.
The best solution is probably to keep a server or a network storage of some sort dedicated to serving files (e.g. Apple's Time Machine is a nice example of this).