It does revolve around energy. Its just because steel is so much lighter than lead, in order to get that same sort of energy, you need speed to compensate for the lost mass. Fast steel still isn't what any of the high density non-tox loads are as far as killing power, but they are much more economical and work just fine for many hunters. I shoot an HD load, backed up by two steel. Most of what we get are singles anyway..and I'm not greedy about shooting doubles. Rarely if ever have to sleuce a bird after hitting it with Hevi, but if I ever do...I will be shooting it with a cheap hevi-steel load instead of an expensive hevi-shot load.