I will also expand on what I said.
I'm not saying steel can not be an effective and adequate killer, it is. However if you compare apples with apples, and look at some of the fast buffered lead loads that are of a similar price point to steel they will perform better (where you can use them).
If you can stand the price pain then tungten is even better, able to be driven fast with very few flyers due to deformation and depending on chemistry even denser than lead.
To answer the OPs question?
Speed is good but not at the expence of density.
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