Cat Gender and Age 

If cats are neutered there is little difference between a male and a female. Neutered male cats can be more indolent than a female. If you already have a cat then going for one of the opposite sex would be a good idea, as a cat of the same sex may aggressively defend its territory.

Once a cat has been neutered its more likely to show its true characteristics.

Male cats are generally larger than females. The largest car pedigreed variety is the Maine Coon cat from the North-eastern United States, where as the smallest cat is the Singapura (or the “drain cat” of Singapore), but breeders take care to make certain their cats fall within the minimum weight range to ensure good breeding. 

It can be easier to give a new home to an adult cat rather than a kitten. Especially if the cat has been obtained from a welfare source as it will have had rigorous health checks. An older cat will be more settled and have abetter temperament but you don’t have the fresh start you would have with a kitten.