Just a side note, not that you thought your KE changed I wanted to note that it didn't. Whatever your KE was before switching arrows, your KE remained the same after switching arrows. Unless you take extremes in arrow weight the KE won't change. When you decrease arrow weight, the arrow speed increases, the KE remains, if you increase arrow weight, you decrease arrow speed, the KE remains the same.

Penetration is influenced by so much more take for instance, field tip design. I bury my ACC's almost everything I shoot them into at all but 80ftlbs of KE. If I simply go to a different field tip, the arrow doesn't penetrate nearly as far.

That's just one example.