Retina MBP - Make 1GB (100%) Video Ram available to VM?

I currently have 512MB available to my Windows VM, if I wanted to run a game (rare that I do) is there an advantage / disadvantage to making the full 1GB Video Ram available to the VM.

I know no matter how much is assigned it will always be shared, the VM will never be able to claim 100% of the resources.

But if I do this, will it give the best performance? Should I reduce it down again when doing business tasks that aren't video card intensive?

I don't know how well Parallels handles games, but it's not something i'd ever try in any other VM software.