In my years of handloading,39 years to be exact,the 30-06 will leave the 308 Winchester in the dust,when both are loaded to their full potential.
For example,in my 3rd edition Hornady reloading manual,using the #3031 150 grain Spire Point,in both the 30-06 and 308,the maximum velocity listed is 3100fps in the 30-06,and 2800fps in the 308,and this has been my experience of approximately 150 to 300fps difference between the two on my chronograph.
Now,using the #3070 180 grain Spire Point,maximum listed velocity is 2800fps in the 30-06,and 2500fps in the 308.
Now when both are loaded to standard military specs,they're pretty much equal,however,the 308 is close to max,where as the 30-06 is downloaded.
Over the years,I have thinned down my collection of rifles chambered in 308 Winchester,matter of fact,I no longer own rifles chambered in 308,because I can download the 30-06 to match the ballistics of the 308,but I couldn't load the 308 to match the ballistics of the 30-06.