If you're not gonna be hunting and just tagging along, take whatever you want, any knife is better than no knife. Your buddy will likely have the kind of knife that he likes to use to dress the game in the manner that he likes to dress them.
My idea of a hunting knife is different than what I would want in a knife if I were just hiking, I think of a hunting knife as the knife I carry when actually hunting. We always bring the game back to camp to butcher and skin it, so that's where I keep those dedicated tools.
So, my hunting knife needs to be able to do simple utility tasks, cut bait bags open, cut line, open packages, cut food as well as be able to gut and lightly field dress my game. Where I have hunted I'm never very far from camp or houses of my family or my vehicle, so fire prep is not a major consideration in my knife choice. It would take longer to get a fire ready and going than to walk to safety in nearly all cases.
What I've found works best for whitetails is a sharp 2.5-4 inch blade. 4 inches is even cutting it close to too big for me. I leave all of the joint popping and pelvis splitting to knives/tools built for those jobs.
I'll likely be packing my JK EWOK this sunday for opening day (if my koyote PSK shows up before that, then I've got a decision, but with Yote in Reno I don't think I have to worry). I might throw a bigger blade in my pack (Koyote Rancher or JK Hiker), and I'll also have some sort of folder (likely a my SAK farmer). Hatchet or axe at camp or in my vehicle.
Thats my take on it, Koyote has an interesting section on his take on knife types on his website as well.
Interested to see what others think.