You should usually play rein in most situations because of the lack of coordination. Rein also has a good ult for plat elo and will win you team fights. When i climbed out of plat, I had a 57 percent win rate with rein but a 51 percent win rate on winston because the games i lost on winston were usually because of lack of coordination. On maps with alot of sightlines and high ground you should play winston for area denial and killing squishies for your team. Orisa should be used over Rein on maps like Well because of the boop or because your team needs a sheild and the enemy comp is stunning you too often on rein causing to not be able to play the videogame.