if you take the shot,and it is over 100 yards,let us know if it broke bones,and if not how long did it take you to ketch up with it,and let us know if it was a one shot kill.Well since energy is biased toward velocity, sure, it is probably more useful in comparing cartridges with roughly the same velocity.
For the record, I don't think a .243 is a better elk gun than a 7mm-08 or 30-06. But I'm not sure it is as inferior as everyone claims. I have a friend in his 50's who has killed an elk or two every year for the last few decades with a .243. He started shooting one not as a stunt, but because he was recoil sensitive. He claims his first 18 elk fell to one shot each. That was back in the 1980's.
I've decided instead of trying to make guesses based on my experience with larger calibers (for the record I killed an elk this year with a .300 Wby.) I'm going to try killing one with a .243 and make judgment after. I ordered a bunch of 95gr Partitions from shooters pro shop today.