Omni and Kalitta get compared quite often (and fair enough, the Omni contract smells a LOT like "K4+0"). But they're pretty different jobs, AFAICT. Kalitta flies cargo, flies a lot, and Connie calls his own shots, for better or worse. Mostly better, it seems like. Omni flies people (people wearing boots, mostly), flies not a lot (at least right now), and is owned by ATSG. Pretty different lifestyles. I'm extremely happy at Omni, because I'm lazy and old, and guarantee works for me. If I were a young hard-charger who wanted to stack the greenbacks and build the hours, I would prefer Kalitta. Caveat Emptor and all that.
PS. I will append that Omni's work-rules are better in some areas simply by virtue of not being subject to the "cargo cutout".