‘Tabby’ and ‘Maine Coon’ are are two different subjects. You can’t compare them because the word ‘tabby’ describes a type of coat while ‘Maine Coon’ describes a cat breed.
There are many beautiful brown tabby Maine Coon cats. There are millions of tabby random bred cats. The tabby coat is the most common amongst all domestic cats.
The Maine Coon is a stupendous purebred cat of great popularity. This cat can have many different types of coat under the rules of the cat associations (the breed standards). Some say that this breed of cat looks best when the coat is a brown tabby-and-white.
The tabby coat is inherited from the North African wild cat it seems to me as the domestic shorthair’s spotted tabby coat is not dissimilar to the coat of the North African wild cat.
There are many other popular coat types and patterns including: tuxedo (black-and-white), tortoiseshell, pointed, gray, black, white, solid colour and white and tabby-and-white.
To recap: the difference between tabby and a Maine Coon is that the former describes a coat and the latter describes a cat breed.