Can anyone pls advise pros and cons of doing this?
Pro are you have an extra copy of the VDI (VM disk) file.
The Cons are only getting a crashed consistent state. That is if you VM crashed and rebooted, that would be the state your copy of the VDI.
If you are making a periodical copy of your physical machine without shutting down, you are better off hibernating the VM then making a backup for consistency's sake.