I have and love my Companion. This is one tough knife. I second what both farmboy and Alberta Ed said. I keep this in my "traveling" vehicle, the one I use for family road trips. I have every confidence that I can deal with most emergencies on the road with this. Those that can be dealt with a knife, that is. It has lots of belly, and a slightly hollow grind, or so it seems. It's almost a high flat or high saber grind, depending upon how you look at it.
The Crewman, as I understand, is basically a short CU/7. That would be a high flat grind. Very good knife also, probably a little thinner.
You are correct on the sheaths. The Companion has a nice kydex sheath, and the Crewman has a nylon sheath with a kydex insert.
If you're looking for skinning, or more delicate knife tasks, then the Crewman is probably what you want. The Companion is a brute. The steel on both is great.