I own a small and medium Carson model 4 and a Sawby Combat Utility. Both are really great knives but they are very different. The model 4 is a standard liner lock that is very well executed with a good lockup. Carson's knives also come in a variety of blade styles, notably both drop point and clip point styles are available. These blade styles are good all around utility and hunting shapes.
The Sawby Combat Utility comes with the self lock which is a very reliable lock that works on a completely different principle from the liner or integral locks. I can't understand why this lock has not been adopted by a major cutler. Sawby makes a knife that is absolutely second to none in quality (no slam intended on Kit Carson at all). The Sawby is made from an integral piece of steel and is incredibly thin but strong. The scales are dovetailed and fit seamlessly. The Sawby is also completely ambidextrious with a reversible clip. The handle is rather long for the blade, which may not please some people. The blade is a hair under three inches but the overall length of the knife is 7.5" while a small model 4 has a blade of 3 or 3 1/8" in a package that is 7.25" overall. The blade on the Sawby is a sort of reverse tanto like that found on the Benchmade 940 with a bit more belly. It has the advantage of a very strong tip that can be used alot of ways. Both the Model 4 and Sawby Combat Utility can be had in a variety of steels including S30V (my Sawby is ATS-34). That said, my Sawby is bead blasted and is pretty rust prone. If you order direct from Sawby, have the blade satin finished, if possible.
Ultimately, chose whatever you like. Personally, I carried both my small Model 4 and my Sawby (plus an A.T. Barr wharncliffe) today. I don't see how you could wrong either way.