Unless a company outright says they use harder steel and their chains last longer, I wouldn't believe it. Most companies will say it's proprietary coating X that increases chain life. I have no intention of trying to test how many miles a coating adds or doesn't add.

The only noticeable jump in coatings I've personally noticed is plated and unplated, because unplated rusts, and they tend to be cheap corner cutting chains.

The trick with the plumber's wrench (really pliers, like channellocks) is to stick the link in the jaws diagonally and press on the corners with the fixed pin and not the slots. It helps to use a paperclip chain hook thing which most people use for joining chains.