I've recently revived my interest in 110's. I bought one back in the late 70's and wanted one just like I had back then. I found 2 on the auction site for a really good price. They were both 2 dots with the 440c blade steel. I also picked up 2 more in a trade the same week. One of them is the newer Bass Pro shops model with the 154cm blade, and the other is an older late 60's inverted stamp model. I would have to say the newer styled handles are possibly more ergonomic and feel better to my hands than the older squared edge handles. I guess if I was going to be using one for an extended time, that would be an improvement over the older handle style.
Other than that, I like the older models because they have the 440 blade steel and they remind me of my first one! I haven't owned a late model with the 420 blade steel, so I can't really comment on the cutting performance between the later and earlier models. I'd love to hear from some of the more knowledgable Buck collectors here and see a comparison of cutting performance between the new 420 and the old 440 blades. That would be interesting! Of course the variables of easier to sharpen vs. harder to sharpen, and the edge geometry would be brought into the argument, and It would probably come down to whatever works best for the individual user!
As for quality of new vs. old, I think they are still built as well as they ever were, and the warranty and customer service is something that keeps knife users coming back for more! It's probably the most knife for your Buck that you can find.