My advice?
BEWARE Amazon as much or more than ePrey.
I'd suggest buying direct from C&C (they are the only ones I know of that regularly stock the 110 and 112 (and a few Buck fixed blades) with 5160 blade steel.)
Amazon closed and locked my account today, because I filed a dispute with the bank over their charging me twice for a couple orders --- after the items had been delivered. (Amazon does not ship anything unless that item is paid in full.)
I don't mind paying for things I order. I expect to pay for them. However, I don't think I should have to pay for something two or more times. Once is enough!
As for your question of 420HC vs 5160, I think I would go with the 5160, if only because I like carbon steel and the way it takes a patina.
Buck does a good job with the heat treat of whatever blade steel they use.
From what I understand, all their blades get the BOS heat treat, even if it isn't stated on the blade.
I don't have anything by another maker with 420J2 (what Buck uses in the offshore made 300 series and possibly some of their other offshore made knives) to compare it to, but the Buck 420J2 used in my 371's and 389, seem to hold an edge as well and as long as my standard production 301 with 420HC blades, and my not Buck knives with 440A blades.
(obviously my 371's and 389 don't hold a edge as well or as long as my 2018 BF 301, and SK Blades Smoke Jumper 110 with CPM154 blades, or my SK Blades Lil' Jack 112 with a D2 blade.)
Enjoy your new Buck!