The accuracy potential of the 308 over the 3006 more than makes up for the 100 FPS loss to it.
In this sport accuracy is everything.
Can an 06 be made to be shot accurately? Yes. Can the 308 do it easier and more concistently? Absolutely. She is much less finicky.
Anyone who would argue against these claims has never worked extensively with both side by side.
There is a reason major branches of LE and military use the 308 over the 3006. Any monkey with 1/2 a brain can do amazing things with a 308 with even minimal training.
Long range shooting is a process that ends with a result. Once you start to focus on the result (where the shot goes, how big the group is, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.