Steel has been the biggest change for me, handle length has stayed between 3 1/2” and 4 1/4. What I carry has changed a lot, at one time I wouldn't carry a single blade knife. When modern knives first came out, I didn't see any thing there to bother with.
The first knife I bought myself in the late 60's early 70's (date varies depending on my memory) was a Case stockman. I came to hate that stainless. I experimented with Buck and Camillus stainless, it wasn't much better. I eventually settled on a large 3 7/8” to 4” Camillus or Old Timer stockman in 1095 and a smaller Buck cadet as a clean backup knife.
That combination held, with an occasional pattern experiment for the next 20 plus years. Until I tried Queen Cutlery's D2. Enter rabbit hole. That led to a mega experiment the Benchmade mini Barrage 586 with M390. The assist only lasted a few days but the knife is still a favorite. At this point I had to rethink these new stainless steels, maybe they're not all bad. In fact I love them, no maintenance work keeping the patina at bay. Absolutely love the edge retention and learning to sharpen these steels has opened up a whole new aspect of the knife hobby that didn't exist in 1970.
One thing that hasn't changed, is I like a knife that fits my hand. I could cut a large double wall cardboard box with a Case peanut but why would I want to? A larger knife with a more comfortable handle just makes the job easier. As long as the blade geometry is good, I'll take comfort over minimalism any day. Tiny knives, I have no use for them.
Of course I'm not young and I do have a bit of dinosaur in me. First rule, knives cut and slice PERIOD. If a blade wasn't designed for that, it's a paper weight, I own pry bars and I don't want them to fold. Deployment speed is a conversation that's lost on me. James Bond's martini is Shaken, Not Stirred. My knives are two hand or rolled open, not flipped, not deployed. That stupid box isn't going any where, whats the hurry.
These are the knives that get 90% of the carry time these days. One in a belt sheath and one in the RFP, it's been the best combination I've ever found.
In a belt sheath it varies more, a De-assisted 586, 486 Saibu, 565 mini freek, Manly Wasp and Lionsteel Bolus clip.
In the RFP, most times it's a Lionsteel barlow. Sometimes a GEC Churchill, single blade Railsplitter or other single blade or single spring traditional, just because.
I'm currently liking heavier folders, by which I literally mean heavier, not 'overbuilt'. So, the Spyderco Shaman, the Fällkniven PXL, the Benchmade Crooked River, the Buck 110 in micarta and CPM-20CV. These are all currently pleasing to me partly due to the heft. Can't explain why, but they do also all happen to be excellent, functional knives. Conversely, my outdoors fixed blades seem to have gone in the other direction, as I am favouring less hefty knives these days. It's as if they are all trying to meet somewhere in the middle! Perhaps it is merely a sign that I am totally middle-aged... 
