These are my thoughts based on somewhat limited personal experience (design, comfort, performance, rust/stain resistance - all the focus of my learning thus far) and my opinion based mostly on research (toughness, edge holding, ease of sharpening) that I cannot personally confirm because of lack of skill and experience (I am almost inept at sharpening, I get there, but only eventually) and/or lack of personal testing in that regard thus far.
Steel:
My steel preferences:
Large Busse choppers mostly for the properties of INFI
Small Swamp Rat for the properties of SR-101.
INFI is good for choppers because it does not chip and the edge can be easily restored. It is more stain and rust resistant than SR 101.
It may not be unanimous but you will find many that say SR-101 holds an edge better than INFI. I have not tested it so cannot comment from my experience.
SR-101 is not as stain / rust resistant as INFI and some will say that they will not own an uncoated SR-101 knife. While I agree that they are more prone to rust and staining, I live on the coast and I own factory satin and home-stripped SR-101 and with proper care I do not find rust a problem. It discolors over time but it looks good that way anyway.
Some would prefer a harder version of INFI for better edge holding in the smaller knives. Jerry has hinted that they are developing INFI NQ for that purpose.
Until then, INFI is acceptable to me in that regard as long as I like the design of the knife - e.g. the CABS.
I cannot comment much on SR 77. I have only owned 3 Scrap Yards, one of which I sold early, one with minimal use and the other is INFI.
Design:
Here is where my thinking was for the most part, but it has started to change recently.
Typically I prefer Swamp Rat designs over Busse designs for smaller knives, mostly because Busse more often than not have a rear drop / heel / talon on the handle e.g. Mean(er) Street, Active Duty etc. While they are super comfortable in standard grip, they are not in all other grips, especially chest-lever grip where the heel digs into your palm. Some like the Game Warden has rounded handles but in many small Busse, the blades tended to be too thick for my liking.
That has started to change recently with some more versatile handle designs and thinner blades like the CABS, SAR 3 etc. from Busse. Also encouraging is that recently Busse has offered choices re. choil or not for different preferences and that makes them more attractive for many, including myself, especially in the smaller sizes. Just in that regard they may become preferable to me over Swamp Rat, that has very little, if any choiless options.
Friends with Benefits:
Apologies if this is not applicable to you, but it might be useful to others just starting out. My best advice is to try many of them for yourself and make up your own mind over time. Don't buy a knife thinking that you have to get it absolutely right the first time - there is too much anxiety and expectation attached to that. Relax and see it as a process and you will enjoy the the hobby much more. To me there is more satisfaction in trying a knife and knowing I don't like it than forever wondering whether I would or not.
What I initially thought was a really ugly knife, with its unattractive cheap looking rubber handle, a knife too cheap to be worthy of being a top performing Busse, turned out to be my favorite Busse of all time - the B11. I would not have ever known that by looking at pictures on the internet, or just reading others' opinions. I took a chance, despite my prejudice, and I am glad I did. Now somehow, it is also beautiful.
Mostly, this is a great group of people on the Busse & kin forums. You might even get to the shows and make some real friends along the way. Well that has been my experience anyway.
The RMD is not a bad place to start:
