should I start my own facebook group for my niche or join another one if the other groups are started by other coaches?

Would it be better to start my own Facebook group for my niche rather than join one that someone else (often another coach) is moderating? I ask because it seems many FB groups have rules about not marketing, and I know I can be helpful and not directly market, but it also seems the people who start the groups are coaches themselves and I am not sure if there’s a more effective way to do it.