Oh my gosh, all of these POV have merit to me. They all capture different angles of the love and loss that both men experienced.
To me, during the time that he lived, Jack had the deeper sorrow. He knew that what he felt was love and as much as he may have known that Ennis loved him, he also saw that Ennis would never take the leap to make a life with him and had to live with the scraps of the sweet life that he was always able to see for them in his mind's eye. Ennis, on the other hand, had built his life on the theory that what couldn't be fixed had to be stood and in keeping with this idea created a wall around himself that allowed him to avoid facing those deeper feelings and acknowledging them. There are pains that you can get so used to you almost don't even feel them anymore. You develop a numb barrier to the pain. Ennis kept his head down for so many years that except for the times he spent with Jack, he never even allowed himself to contemplate any other possibilities.
Once Jack was gone and Ennis' heart was burst open with the discovery of the shirts, his became the greater sorrow. Because Jack is finally at peace, whatever he may have felt in life, and Ennis has to endure without him, knowing at last what their love was all about and knowing that every chance he had to do anything about it has passed. He has learned valuable lessons and is applying them to his relationship with his children, which is in itself a gift, but side by side with the nourishment his heart gets from knowing how deeply he was loved is the regret and loss that can never fully dissipate as long as he is alive.
And that is why I'm somewhere between the people who think he was happy at the end of BBM and the people who think he was miserable. I think that he was damned to walk the line between the two for the rest of his life because the knowledge of the love brings at the same time the happiness and the devastation that he can't help feeling when he thinks about Jack.