I feel it depends on how Ennis feels inside about each of these partners. IMO during the scene when Alma confronts Ennis at Thanksgiving, Alma is clearly getting under Ennis's skin, calling Jack out of his name and alluding to what they do as "nasty". She is obviously holding a grudge against Jack for destroying her marriage and is playing her ace straight up. At the same time she opening a can of worms in Ennis himself, what he will not, cannot admit to himself and going years, back revealing her suspicions to him. But he feels for Jack, his friend and lover and stands up for his honor in this confrontation with Alma. She was pushing all the wrong buttons.Too scary.
With Jack, Ennis feels an emotional connection. Jack appeals to Ennis's sense of manhood that expresses his protective nature so anything Jack does or says is for both their benefit. For instance the scene in which Jack refuses to eat beans again and suggests shooting the sheep. Ennis compromises and goes for the elk. Jack had meat for dinner and breakfast. Problem solved. This becomes a pattern with Ennis. He gets mad at Jack but can't stay mad, as he finds out, Jack is uasally pushing all the right buttons but makes Ennis think in a constructive , positive way and most of all he loves Jack deeply so he's more patient towards him.MO.