Super-Large, because it gets the higher ATK/HP/DEF, sure its speed is the lowest but its not like its going to be the fastest on your team even if you decided to go with the small. My Super-Large can actually fend well for itself.
Just do what I do man, have a team of many rotating Pokemon. :'D It may take more time to train, but its totally worth it in the end. You get to train all of your favorite pokemon and you have strength in numbers when taking on gyms. (For example, I had my Talonflame, Charizard, Blaziken and Vivillion when taking on the grass gym. :'D )