I'm a 243 owner , shooter and hunter. Never been under gunned for what I use the 243 for. (WT, Mule deer, Pronghorn, Black Bear, Cougar and all the different varmints) use 100 grn on Big Game. 75 grn on the varmimts.
Is the 6.5 really that much better? Buddy of mine says it's the best caliber for all hunting in the lower 48. And says he believes it'd make an excellent African plains hunting caliber for all the thin skinned non dangerous game they have.
If I want more HP. I go with my tried and true 06.