Parallels does have a Pause button for the VM. It dims the window for the VM, and I notice my MacBook's fan speed lowers after that, so I presume that means that fewer resources are being consumed. I notice that my OS X apps run faster as well after pausing Windows.
Nice! I didn't know that, thanks.
now if they can also do it the other way around, a pause button for the OSX it would be great.