Mobile & manufactured homes can only be placed in areas that are zoned for them. They have wheels and a frame beneath them, which are usually removed during setup. But modular homes are assembled in pieces. (Not like a double or triple-wide that is just connected) Modulars are brought to the lot where they will be placed, in sections. Each wall is connected to another wall, one piece at a time. Modular homes can be placed in residential communities. They don't need the special zoning.
Now, if you're asking about the difference in manufacturers, you have to think of mobile and manufactured homes like cars. They have a make, model and serial number. And just like cars, you have your high and low end brands. They also depreciate like cars. When you buy a car and do regular maintenance on it like changing the oils and tires, replacing what breaks, etc., it's still worth less than when you bought it. The longer you have it, the less money it's worth. The only way to avoid this with mobile and manufactured homes is if they're placed on your own land. Land does not depreciate. But it may not appreciate with a mobile or manufactured home on it, depending on how long you own it, how well you maintain everything, and what the surrounding area is like.
I hope this helps. I don't sell very many of them anymore, but the basics haven't changed. And one more thing. When you buy a mobile or manufactured home, you have to pay tax, tag and title, just like a car. With modular homes, you do not.