Insurance in Michigan is...expensive. You already know that!
In my opinion, the main advantage of a motorhome over a trailer is the much more convenient access when on the road. It may not seem like much on paper, but having your house stuff right there in the vehicle with you is really convenient. If you need to use the bathroom and it's raining, no problem--just pull over someplace level and do your business. Similarly if you want to get a sweater or a glass of water or what have you. If you're traveling with a few people, there's more elbow room than in most tow vehicles.
A secondary advantage, over a trailer, is quicker making and breaking of camp. It's not a massive difference in the grand scheme of things, but it is something and those minutes can add up if you're traveling often. A third possible advantage over many trailers is that there's a generator built-in, and maybe greater propane capacity with a built-in tank.
The disadvantages are pretty obvious: it's another vehicle to maintain (and pay for tires, etc. for). If you don't tow another vehicle, you're limited in your options for getting around from camp for sightseeing, shopping, etc. If you do tow another vehicle, you have the hooking and unhooking and maneuvering of that combination to deal with. Fuel mileage is not great--though that's likely not a huge expense in the grand scheme of things.
As for a class C vs. a class A (or a class B), the differences are less pronounced. A class B will be much smaller, an advantage when you're maneuvering and a disadvantage when you're trying to cook or bathe or whatever inside. A typical diesel pusher will be quieter and more comfortable when on the road, due to the rear engine that's much farther away and the air suspension system, but a gas class A and a class C are rather more comparable in those areas. If you find a layout that's ideal for you in a class C, the big advantage of the class C is that you get the layout that is ideal for you.
Personally, I'm very happy with my class C motorhome, and travel without towing another vehicle.