From my deployment days with the USAF 1979-2005 I carried a Gerber Mark I in my boot everywhere I went. And for an AF guy I went all over since I was in a Forward Air Control unit for quite sometime. I did 16 years overseas.
If I were going to choose between the RC-4 and RC-5, I would go with the RC-4. The size is just right for doing most tasks if your not looking to chop your way through the jungle. It's size also gives you lots of options on where you want to carry it. In most locations it won't be in your way. It's very sturdy, holds and edge and sharpens easy IMO.
That said you should get an Izula as well, nice and compact, but a hell of a knife!
Thanks,