It’s kinda a preference thing. But Imy money is (literally) on MC. Bigger is not better.
My son loves MC and has seen the most improvement there, but ymmv. I think the biggest difference is that MC does all of their classes by skill level rather than age, if your child can handle playing with the bigger goalies, they will move him to the right class.
Its personal preference but I would tell you my son goes to Stop it and the same goalie coach at stop it for years and loves it. He also goes to another goalie coach i believe its nice to get a mix of a couple different. Differnet drills maybe a little technical difference and then its really up to your kid to take the tools and figure out what works for them