Yes, energy matters, but you can't draw a correlation between between energy and shots that stop a living thing because there are:

1) Other ballistic variables

2) Way too many different shooting situations and targets

Even if you just count C.O.M. shots at head-on human targets (just a ferinstance to narrow it down) you will still get different results because there are WAY too many variables.

Someone told the story about the woman who killed a Grizzly with a .22L rifle. I AM NOT going to hunt Grizzly with a .22L rifle. I want something with a bigger heavier bullet of the proper type, moving at a good rate, which incidentally, will have more energy.

I'm not going to choose a gun for any purpose solely on it's energy, but more on it's reputation and results of testing. I could easily say, "If more energy is better, I'll carry a .50 Desert Eagle" but I much prefer something in the 9mm to .40 S&W range.

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"He was kinda funny lookin'"