If I was a crazy guy who enjoys human meat, then I'd probably take that St. John brother who's extremely creepy... Ehh... Danny? He's good with guns and he can scare everyone just by looking at them.
But since I'm a normal person, I'd pick
Carley and
Mark.
Carley:
- Good and interesting personality
- Reliable
- Trustworthy
- Good with handguns
- Good physical form
- Looks good
I know that Carley would back me up if something goes wrong, I know I can trust her with my life, I know that she would shoot walkers right between the eyes and that she would not fail any jumps or climbs. And I would be pretty nice to her, ahem.
From the survival point of view, that's a perfect companion, at least for me.
Mark:
- Good personality
- Good intelligence
- Reliable
- Trustworthy
- Good physical form
- Cool glasses 
- Good with guns
Again, Mark is a reliable guy whom I can trust, he knows how to handle a weapon pretty well, his coordination skills are good, he is intelligent and rational most of the time.
A team like that would be able to survive.