Buck has always done a good job with heat treatment and edge geometry has more to do with performance than steel, if all are properly heat treated for best performance. I have not used the 420HC in bigger knives like the 110, only in small knives like the 301, 302, etc. The 425 was great for a wilderness knife steel. I "prefer" the 440C and even more the 154CM (not only for edge holding). There was nothing wrong with 425 as a low end steel, but I was glad when they moved on. My 110 in 425 "took a lickin' and kept on tickin'" as the jingle went. I have a photo of this one somewhere and it shows the use. My 440C I passed to my nephew. It was from the 1965-1967 time frame (I cannot remember exactly when I got it but '67 is the latest possible date). It is amazing how these knives can be used pretty hard (not abused) and still be passed down through generations. Bucks are a treasure.
I remember as a boy, I was looked at in awe because I was the first one to get a real Buck Folding Hunter. It was so sharp from the factory that a boy admiring it cut his hands in many small places without realizing it while looking at the knife. (Duh!). I took that knife camping and opened metal food cans with it, dug out roots, cut down small trees (the proper way by cutting and not chopping) building shelters. We prided ourselves on not using tents, but rather, building our own shelters in the wild. That knife skinned deer, fox, rabbits, ducks, catfish, and snakes. It whittled, and helped me wile away the time sitting on my grandparents front porch whittling on a large limb. It cut sugar cane (tough stuff) and carved pumpkins. I have a lot of fine memories in that knife and it stayed sharp, too.
Later, on our farm, as I was older, I used it for farm chores. I finally replaced it with a newer one in 425 (why I cannot remember) but kept it as my camping knife. It was funny, I would carry a fixed blade but that 110 was always in my back pocket. It never left my back pocket as a teenager roaming with my friends. When I joined the Army, a 110 was always with me. Great knife and no other knife I have (many) has as much value to me, nor memories.