I've never understood this argument. You're aware that people can, like, take the jackets off to fight, right? Like, the jacket is not glued to your body? People preparing to fight generally remove extra bulky layers to avoid getting hockey jerseyed, it takes just a second to throw your coat off.
Jake Shields is about a billion times better MMA fighter and overall grappler than Yan Cabral, and he trains no gi exclusively. You know, the guy who beat Maia in a pure grappling match, has a win over the current champion, tapped out Lawler etc. Same with Josh Barnett. When will these terrible pro-gi training arguments from 2007 disappear? It's just the same three logical fallacies repeated over and over and over....
I've lived in New England my entire life, have a whole closet full of winter clothes, and my gi is much more rugged than any of them except maybe for my heaviest winter jacket. I find it very, very hard to believe that much of the stuff you do in the gi translates to 'real world' clothing like sweaters, sweatshirts, any type of lighter jacket etc. (Also relevant, I'm a blue belt, not just theorizing about gi training)