First things first! Whether you choose to adopt a male or a female Maine Coon, do it for the right reasons. Breeding cats is an expensive hobby that does not really ever turn a profit, so do not adopt with the thought of breeding in mind. It takes years and years (even decades) of experience to become a responsible breeder.
Whether you adopt a male or a female, do get them neutered or spayed! Neutered or spayed cats are healthier cats and of course they are much easier to live with. The differences between the male and the female of this breed are not great, although there are some clear differences.
Males
The male Maine Coon cat is bigger physically than the female and they also tend to have bigger personalities. They are more demanding as far as “mommy or daddy and me time”. They are very social and they want to hang out. They need stimulation and plenty of play time. They are curious cats that actually like people (yes, it is hard to believe that there is a breed of cat that does more than tolerate people).
Males are a bit more needy in the amount of space that they take up because they can be a few pounds heavier and all around larger than the female.
Females
As stated above the females are a bit smaller than the males; it may not seem like much but a few pounds and an inch or two can be a big difference if you live in a smaller space. The females are also a bit more cautious when it comes to "letting loose" around people.
They are outgoing and friendly, but not to the extent that the male Maine Coons are. The ladies are a little more reserved and laid back. They are both generally such super nice cats that ultimately it makes no difference whether they are male or female.
Overall
At the end of the day it really is a personal preference. If you want the larger cat then go for the male, if you would like one that is a little more mellow then the female will suit you. It all comes down to what you personally prefer.
In both the male and the female you are sure to get a cat that is full of personality, fun to be around and loving. The choice is absolutely personal!