I had a Ruger 77 .35 Whelen loaned to me to develop loads for it for about a year. For the lack of enough .35 Whelen brass and having a mountain of 30.06 it was very easy to form Whelen just with the Whelen dies. I did not notice any difference in performance between the 30.06 formed cases or the actual Whelen cases. Not real extensive testing but the recoil did give you the sense there was certainly a bit more energy there. I did take a whitetail with it. Did not have it long enough to take it out a it farther to 200 or 300 yards. I believe with the vast choices in powder out there one could certainly come up with some very effective loads with some time spent testing.
Around here there are 243,270's galore. The 6.5 Creedmore is going to cause some of the old favorites to gather dust.