I don't own a Malkoff, but seeing what people say about them, I think I know why people like them. These US-built flashlights are overbuilt. They are basically built to serve a lifetime and survive the most extreme use. Malkoff examined and researched the vulnerabilities of flashlights and designed his to be overbuilt so failure is less likely. Not surprisingly, he seems to offer a lifetime warranty on Malkoff products. Basically, the difference is the quality in which they are built. Sure, they aren't the top spec products for output, modes, etc. but they are made to work each and every time for basically a lifetime. While these qualities may not really be of the most importance to a regular owner or even the flashlight hobbyist, I think it resonates well with those who use flashlights for duty like military, police, security, inspectors, etc. Furthermore, US-made flashlights are often designed with firearm mounting in mind. This means they are built to withstand the recoil from thousands of shots.
So again, products like Malkoff, Elzetta, etc. are overbuilt to withstand and survive the harshest conditions a flashlight may encounter to offer top reliability. This means they need the best quality in parts, design, manufacturing, and after-service. Hence, the attention is on that instead of chasing the top specs in lumens, run times, modes, features, etc. Given many US-based flashlights cater to military and police clients, they are built with reliability as a life-or-death difference so their products are designed not to fail.