Muman I think sterlizing animals that are way overpopulated and this is causing tragic situations (like dogs and cats) reduces suffering in the world. The most important ones to sterlize among them are females too.
Among the feral population outside I've taken 4 cats in, in addition to those I got 3 females and 2 males sterlized. This was a good thing, otherwise the females would be having one or two sets of babies every year and in this neighborhood most kittens die that are born outside and those that dont' tend to have a hard life with no house to live in. It helps the males because they don't get into as many hormonally-driven fights and live longer injury-free. They are also not able to impregnate females this way but still patrol their territory.
One of the males I think may have died because he disappeared not too long after we released him. The other stayed around for a long time and then disappeared, not sure where he is. The three females that are outside are still coming around every day or almost every day and what's wonderful about that is two of them are a mother and a daughter. The mother Blackie has been able to keep a friendly relationship with her daughter Smokey because she didn't have litters and litters more of kittens, and so they're able to be a lot closer than they would be otherwise. They're often playing together or eating together, etc. If Blackie would have had a lot more kittens then Smokey would have by necessity been pushed aside.
I've seen a lot of dogs and cats that were dead hit by cars around the area, and I know there are mean people who would do bad things to them too, so it's better if more than necessary are not conceived.