I had my male Will, who is an outside cat, neutered at about 1 year old. He was born at the farm across the street, and he moved over by us on his own. He is our alpha cat, and in charge of the 4 acre property. In a way he is my cat, but then again he is a free spirit who chose us rather than me chosing him.
I have the greatest respect for this cat. I love him dearly, and he makes me smile every time I see him. While I consider my inside male, Garfield, to be my cuddlebug baby, I consider Will differently. He hasn't acted like a baby since I met him, and he was probably 4-5 months old. I just see him more as an independent guy than a pet.
Will is in the garage every morning, at at night when I come home. But during the day he leaves, and makes his kitty rounds. I honestly have no idea what he does all day, but he has a busy life.
I did neuter Will, and regret that I waited so long that he was in 2 severe cat fights, causing injuries. His neuter made no difference in his personality. If I don't pet him enough, he still grabs me around the ankle with his paws as I walk away from him. He still makes his rounds, he still runs off any new cats.
The changes I have seen in Will are that he tolerates my other cat Josie much better. He has not been in any fights that I know of, although there are occasional yowling matches. He has had no injuries from an actual fight.