you should go with neither. How many addons are you running? The spec of your machine is light years above mine and I get 45 fps on main window everywhere but heavily populated areas. It is very playable for me of course I dumb down my graphics to min on slaves and about mid range for my main. You have made some great choices on your computer specs it is much of what I want but I would probably OC the processor with appropriate cooling. That is just me I am an OC'ing nut.

I have maxFPS on my main set for 45 fps and bckFPS for slaves at 20 fps. Works great.

Both Ashenvale and Strangle are heavy on the textures perhaps the high environmental and clutter detail is hosing you up?