When he thinks of Emily, he thinks of muffins
He thinks of domestication and coming home to the perfect housewife that greets him with a bunch of cookies and smiles. He sees the Uley family twittering around in the backyard. He lives the stereotypical American dream.
She gives him dominance, she gives him the final say. She makes him superior. She gives him breakfast with a smile, and always has the house clean.
He pecks her on the cheek, before he gets ready for the work. He ruffles the hair on his second son's head.
He sees this, when he thinks of Emily.
When he thinks of Leah, he thinks of possibility.
He thinks of rebellion and constant arguments. He thinks of conflict. He sees himself coming home to nothing but an empty house, and waits hours for her to show up. And she does so with a grunt, but the love in her eyes is plain to see.
He sees the Clearwater-Uley family, filled with courageous and self-respecting (or maybe even, self-righteous) daughters that so strongly resembled their mother. He sees a not so traditional, yet equal household. He sees disagreement, but compromise as well.
He sees this when he thinks of Leah.
And being raised by a single mom himself, he knew which scenario to prefer.