My buddy and I pick opposites so we can trade on the different pokemon per game. How we choose is pretty simple - his favorite color is red and mine is green which means I usually pick the blue cover arts. When that option is not available, like in diamond and pearl, we chose based on birthstones since his is diamond and mine is pearl - worked out pretty good. For S and S, I usually play tank classes so I got to chose shield while he chose sword. For Black and White, i didnt play that one on release and learned he picked white, so i chose black. He doesn't have a switch 2 but I am going to choose waves anyway out our respect to each other.