BG42 is really an excellent Stainless. I wish it was used more. REason for not being used are probably price, availability, temp required in heat treat, etc.
IN stainless, thre are two that really stand out in my mind. 12C27 for softer blades where I want toughness (for stainless) and high stain resistance. The second is BG42, run hard like CRK used to. It take a really fine edge, holds it for along time, is decently tough (for a hard stainless, nothing like M2 at the same RC) and provides good stain resistance.
I think Sal Glesser could probably give the best answer of how BG42 compares to S30V. I heard Spyderco really took a hard look at both and chose S30V.
Like you, I wish BG42 was offered in more knives/ For my uses, it is a better steel for most applications than S30V.