Confused about virtulization and GPU usage.

What keeps you from using gfxCardStatus and simply force the Intel GPU.
Usually there are troubles when you switch the GPU while the VM is running. It doesn't outright crash but it is a lot slower than it should be in my experience.
The only thing one can do is restart the VM and be glad is doesn't take that long with a SSD.

force the Intel always unless you mean to play a game or plug in an external screen.

I am not sure I really understand your questions. In any case you can only force the native OS (OSX) to use whatever GPU you want by means of gfxCardStatus. VMWare Parallels don't give a **** what GPU is running. Apple's drivers suck though and thus a restart of the VM after a switch is usually necessary for full performance at least in my experience. It also doesn't matter if the VM that is running is the bootcamp partition, some Windows Image, Linux, Solaris or whatever.

 

The boot camp partition gets virtualized, just like any regular old virtualizing, so no, the discrete GPU isn't being used like booting into bootcamp would, they are two very different things.

 

You'll see an impact on battery life still, virtualizing is RAM hungry and can be CPU hungry at times. You'd have to compare for yourself, but both methods will have a big effect on your battery life.

 

Depends on the workload. The overhead of virtualization can eat up all the savings from the Intel GPU quite quickly by causing higher CPU load.

 

I'm not sure how vmware fusions works but for parallels there is an option to use either the integrated graphics or discrete graphics. I use excel 2010 in parallels off my bootcamp partition a lot and the battery life is not too much of a hit (can still get 4-5 hours of work). This is in an early 2011 2.3.

 

I don't own a MBP with two graphics cards(yet), so I can't really say whether or not this works in either program.

 

Or alternatively, I think you can try to undervolt the 6750M while under Windows so that while you don't game, it wouldn't suck as much battery.

As mentioned, the tradeoff of virtualization is that CPU usage is still high enough, so it pretty much cancels out the power saving achieved with just the integrated GPU. If you have low RAM, it'll also grind your HDD non-stop.