Depends on the type of steel. The tool steel used in Tuffhead Evolution and Iron Wills is more resistant to impact, so it can be hardened more than other steels before becoming brittle.Rockwell- sometimes more is not better In a BH.
Its counter intuitive but tempered steel Heads with a very high Rockwell have been proven out NOT to be the best for bowhunting Due to the hard impacts.
So where its desirable for a processing knife to hold a good edge longer a BH that takes a hard impact can snap. The higher Rockwell makes the steel harder but also brittle ( like a file) There is a sweet spot there for BHs, seems to me its somewhere around 45-50R.
Ive talked to the owner of VPA, those heads hold a very good edge without being brittle at I think somewhere around 45 Rockwell. They
I know a few guys that bought those over tempered dangerous game heads from years ago and the BH broke and failed on buff ribs- tough to swallow on an expensive hunt.
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Tip design makes a different also. I had some Grizzly Stik samurai heads that looked similar to those you pictured and I had a tip break off like that from going in the dirt under a turkey. A flat, unsupported tip isn't as strong as a tanto tip with more ferrule support.