Before making a decision I think you should step back and think about what you want this rifle to do.
If deer is the biggest game you'll be going after, what's the range? The 6.5 PRC is very capable and the 6.5 PRC recoil is more manageable than the 300 WM if both are running heavy for caliber bullets. With the 6.5 PRC, largest bullet available at this time is the 156 Berger, and the 6.5 PRC would likely run this in the 2900 to 2950 fps ish range. However, if you load a 150 grain bullet in the 300 WM the recoil is far more manageable (more akin to the 6.5 PRC) , and you can likely get it moving 3400 fps or more. In this scenario with the 300 WM, the advantage of the higher velocity turns it into a lazer equating to less drop, faster time of flight, and with the right bullet the higher impact velocity inside 300 yards (maybe farther) will result in far more devastating terminal results. If your deer hunting is 500 yards and under, the 300 WM running lighter bullets super fast is hard to beat.
Obviously I prefer 30 cal magnums, the terminal results are far more noticeable than lesser calibers, they give you the option of larger game if you have the opportunity at some point in the future, and their's a wide variety of projectiles available, from 100 grains to well over 200 grains.