I see this is your first post. Welcome to the forum. You'll meet a lot of nice people here.
Here are a couple of threads that might interest you. The first gives my opinion on roosters and the second gives a lot of other people's opinions and experiences.
Number of roosters thread
https://www.backyardchickens.com/forum/viewtopic.php?id=219443
Managing Multiple Roosters
https://www.backyardchickens.com/forum/viewtopic.php?id=229968
As far as mutant chickens, all chicken breeds are crosses from other breeds or actual mutants, called sports. It is genetically impossible to tell one chicken breed from another. We all keep chickens for different reasons. Some people like to keep the breeds "pure". Some of us like what we call "mutts", which are crosses from recognized breeds or offspring of those crosses.
As others have said, whether you keep both, one of them, or neither depends on why you have chickens. If you want to hatch your eggs, you need a rooster. If you are only keeping chickens for eggs or as pets, you really don't need a rooster. If you want eggs or meat, keep the larger rooster. If you want broody hens, that Silkie would probably pass on some good traits.
Some people love their rooster as a pet and some hate roosters. That is covered in the links.
Good luck and again, welcome.