Disease prevention, reducing fights, cleaner home, and reducing pet population are some benefits of neutering male kitties.
After our kitten, only 3 pounds, was neutered a few days ago, I kept him under my watchful eye the first night by sequestering him into the bathroom for the evening. I checked in on him many times and gave him a small amount of food before going to bed. He looked sleepy due to the anesthesia.
By morning, he was awake and refused to follow any of the doctor's orders. He climbed on furniture, wrestled with our other kitties, and jumped. These are all things that should be avoided up to 10-14 days post surgery.
Satoshi is a trooper and his recovery must be remarkable due to his personality and his age.
https://www.hillspet.com/cat-care/healthcare/benefits-of-neutering-a-cat