The marking knife is a deceptively simple tool, much more than just a blade and a handle. It's called on to do a lot in the shop, and the author did a lot with the 16 knives he evaluated. He conducted several tests: 

Scribing, or scoring a line against a rule. Here, Latta looked for cleanly defined lines deep enough to anchor a chisel.

Dovetail layout. Marking dovetail pins tested each knife's ability to strike a line in confined quarters.

Tracing a hinge. This involved cutting with and across the grain.

Marking for banding. This test showed which knives work well cutting toward and away from the user.

In the end, the author notes that individual needs and preferences play a large role in choosing a knife. In this video, you'll not only see how he tested the knives, you'll also see which knives earned his commendation as best overall.