That Depends on what you call a BIG mule deer.
The best state for muleys according to the number of B&C entrys is Colorado.
Utah is also a good state to find a monster but it will take you a few years to draw. Idaho and Montana ans wyoming also have great areas. where you can find some 190 class mule deer.
If you bow hunt Nevada offers some awsome early season high country hunting that is very physical but you see alot of deer.
Another area to consider is Alberta you need a guide but you can find some really good deer.
Eastmans hunting journals every year produce a mule deer hunting
guide that out lines the best areas in all of the westerns states and the chances for drawing a tag. I have used it in the past and found it very informative.
I know this post is very vage but it may offer a starting place