Geldings can be turned out with other horses and enjoy a herd experience. In no way would I ever equate gelding to performance enhancing, it is QOL enhancing. Does it make them quieter and perhaps easier to handle? Well, for the most part, yes. But I wouldn’t do it if I had a potential (dating myself) Popeye K or Abdullah in the barn.
If I had a 4yo with a great jump and lovely movement that had some attitude but might make a nice junior/AO hunter? Yes, but the attitude adjustment would improve his whole life. It would not be because I was trying to adjust his performance. Junior/AOs don’t want a stallion anyway IMO.