lrucker wrote: The 'defaults' tool changes that data which then gets pushed to disk at some point in the future.

Think of it as editing a vmx file for an open VM - the vmx doesn't know about the changes and will overwrite it with the in-memory data.

You're telling me something I already know as I do read the OS X Man Pages!   Aside from that, it's common sense that one only modify settings via alternate methods when the Target is not running.  BTW  defaults writes to disk are usually done in real time, the main thing it to not use it on an open file unless necessary and then use appropriate methods to push the changes to memory when/where applicable!  In a case such a with VMware Fusion one should only use defaults when it's not open.