Medium format cameras are funny because they can shoot like both large format and small camera. I’ve only used Mamiya’s, and my first was a 645 which works alot like an SLR. After that I used a Mamiya RB67 which is bulky and shoots much slower like 4x5. Currently I use a Mamiya 7II which is a range finder and has been my favorite so far.
I guess it depends on what kind of camera best suits your style of shooting. If you’re just starting out I’d go with a twin lense reflex like a seagull or yashica. Those seem to be the most common starting point for everyone that wants to shoot medium format.