What you see is what you get.
When you adopt an adult cat, you know what you are getting. Sure, kittens are cute, but you never know what the future holds. An adorable kitten could grow up to be a really ugly puss. This is a big risk. Go for the sure thing. Take a sweet-faced old Tabby.
High mileage cats still run great.
Used cats aren't like used cars. They aren't at a shelter because they are defective or worn out. They may have simply been abandoned. In those cases, it is the previous owner that is defective, not the cat.
Adult cats aren't as "chewsy".
Kittens are like human children: everything goes in their mouths. Whether teething or just exploring bits of the world around them, kittens can be very destructive little bundles of fur. Kittens chew on shoes, the corners of books, ear lobes, carpet tassels, electrical cords, drapery strings, plants, and much, much more. Adult cats typically chew less, if at all.
Kittens stumble in blindly, where adult cats fear to tread.
Two well known clichés about cats are: "curiosity killed the cat" and "cats have nine lives." And curiosity usually leads to the loss of about 8 of a kitten's lives in its first year. Kittens tend to get into much more trouble resulting in accidents and injuries
Einstein knew the truth about cats.
The genius scientist Albert Einstein discovered an important relationship between mass and energy. He described it using the mathematical equation E=(MC)2. This equation means that your Energy level (E), is proportional to the Mass (M) of your Cat (C), twice over. The equation basically shows that if you adopt a cat with more Mass, like an adult cat, your Energy level will be much higher than if you adopt a cat with a low Mass, such as a kitten. This is true because adult cats sleep more, play less, require less supervision, break fewer lamps, and don't try to bite your toes through the blankets in the middle of the night. With an adult cat, you will sleep better, relax more, make fewer claims on your homeowner's policy, and enjoy more Energy. There you have it. Are you going to argue with Albert Einstein?
Kittens and children don't mix.
Children can be rough on both cats and kittens, even when they mean no real harm. It can't be helped. It's just how kids are. When you tell a child that "cats always land on their feet," the first thing the child will do is drop one from your rooftop to see if it's true. Adult cats are better equipped to deal with pesky kids. They can generally escape from them, hide, and then contemplate revenge by moonlight.
It might be their last chance.