For a chopper I would want lath martensite rather than plate martensite (meaning fairly low carbon), fine grain, and low carbides and low levels of things that don't contribute to the strength of the matrix such as carbides, excessive chromium, nickel.
S7, 5160, 4150 (!) might be very good.
S30V, despite Crucible's claim of high toughness, has never compared to plain carbon steels for raw edge stability. I don't know much about BG42, though I'd still wager plain old 1084 would spank it soundly in a chopper where edge stability trumps wear resistance.
Also W2 and L6 :thumbup:
As much as I like O1 and D2 (very good cutting steels), they would not be my first choice for a chopper unless you're chopping something like carpet or drywall or other abrasive things.
I'll point out, I haven't made many choppers - I make smaller thinner knives.