Size, handle material and color. CA52161 is 3.5 inches closed with a 2.5 inch black stonewash blade and a black G10 handle. CA52119 is 4.5 inches closed with a 3.5 inch satin blade and an orange nylon handle. Both are stainless linerlocks with inlay shields and pocket clips.
CA52161 at 2.5 inches is the compact option; CA52119 at 3.5 inches is the full-size one. Case pattern numbers T01193.5 and T0124.5OR respectively.
That size gap changes how each carries far more than any other difference here does.
Black G10 against orange nylon. G10 is harder and grippier; nylon is lighter and cheaper. Orange has a practical benefit worth mentioning: a dropped knife in leaf litter is much easier to find.
Both carry an inlay shield, thumb stud and pocket clip, with a thumb ridge on the larger knife.
The small G10 one for pocket carry and grip. The orange one for a larger blade in a color you will not lose outdoors.
See the black versus orange comparison if you are choosing between the two full-size versions.
Specifications above come from the manufacturer. Live prices and availability are in the strip below, pulled from the catalog at build time rather than typed into the copy, so they cannot go stale on this page.