Skuzzy,
I have both options enabled and use them both. To get the video ram preload to become enabled I had to drop my texture size to 128.
Even with the preload, my video card still has lots of free memory.
Why is it a problem to use both? I, like others, have noticed my FPS has dropped, but I'll give that up in a sec for the smooth game I have now. The stutters were awful for me before.
I assume from your explanation that pre-loading video ram is better than pre-loading system RAM? If you have a choice it's better to load video?
If using both is not a good idea, perhaps you should add a control to the code that will keep folks from enabling both. Basically only one box can be checked at a time.