One of the great echoes of the "No more beans!" line in the movie shows us just how much Jack matters to Ennis - the very next food run, he asks for soup, not beans. The Basque even reminds Ennis that he had said specifically that he didn't like soup. "Well, I'm sick of beans." Sure, he isn't going to admit that "the other guy doesn't want the beans", but even so, it's quite an interesting response.
I like the idea of Ennis the pragmatist and Jack the dreamer, as you clarified so well, MissisaugaRed. I had labeled them a bit differently; Ennis doesn't rock the boat, and doesn't attract attention if at all possible; Jack questions things, resents unfairness, won't be told what to do, spurns authority. Ennis never had time to separate himself from his parents, as Jack did, so that might have some effect (and I'll stop my pop psychology right there.)
-backtobrokeback