Why more or less shims?

I have been very frustrated with Suspension shops! I have tried a couple and they seem to do everything the way they want it instead of the way I want it. So I have begun doing my own. My son races Cobras and we have tried to get shops to get him more rebound damping (and compression). Two of the shocks that I have dissassembled are set up totaly differently although we were asking for the same result. One has a huge shim stack made up of almost all .006 shims of varying sizes and the other uses .012 and .014 but fewer.

My questions is: Is this preference or is one way better than the other?

Thanks,

Bill