Mostly depends on how long the trip is going to be. For day-hunts or a weekend, I am happy either way. When the hunt length begins to extend past that, my list of acceptable/agreeable hunting partners becomes exponentially shorter. Several times while elk hunting when the weather is gorgeous and I don't have a group bedded to stalk on, I'm quite happy to nap in the sun. That doesn't mean chat about the meaning of life and solve all the world's problems, that means take a nap in the sun and fresh air.
I've got 2 frequent hunting partners that I know I can travel anywhere, hunt anything, and just have a good time with. No jealousy if one guy fills a tag and the other doesn't. No rushing to get something killed before the other guy. No wondering about if the guy is gonna get rip-torn and be hungover for days on end. Just a thoroughly enjoyable trip where the only thing that anyone is really thinking about is maximizing fun.
If I'm being truthful, another major factor regarding a hunting partner, is, can they tolerate ME for any length of time as well. I'm heavily sarcastic, strongly opinionated, and I know that my personality can wear on other folks in a hell of a hurry sometimes too.
The one critter I can truly say that I prefer to hunt alone (with the dog though) is ruffed grouse. I prefer not to have to worry about shooting lanes, staying in line, etc. Just follow the dog and shoot what he flushes.