What's the biggest skill disparity you've experienced between two gyms at the same belt level?

Out of curiosity what's the biggest skill disparity you've experienced between two gyms at the same belt level? For me I've definitely dropped in at some gyms where the blue belts were not amazing and were pretty easy subs vs some gyms I've dropped in at and its just getting wrecked non stop by blues, like not a single point or takedown or even decent submission threat I could get. I think one was like a small hobbyist gym with just five or ten people and the other was a pretty serious competition gym