Using GPU from United
I live between Mel and yyc so the 6 GPU per year allow me to fly family 6 legs on economy W fares and ride in business. It works for this scenario to be loyal to one airline.
I don't fly too many short flights so the accumulated savings from discount would not cover the say $20K I get from the 6 GPU
Just 2 cents for long haul flyers, that being said, the GPU advantage does not get used by me so if I didn't have them I would just have grumpy family!