The female ones do tend to overclock better. Your mileage may vary if you get one from a shelter, as you usually can't ascertain the stepping before you buy, but (jokes aside) you'll be doing a good deed as the poor cat would've probably had to be put down if you didn't take it off their hands.
Slightly OT, but I never got why animal shelters take in cats personally. I can understand why stray dogs need to be kept off the streets as they can be a menace - they tend to form packs and sometimes go feral and vicious, so it makes sense to put them in a pound. Stray cats, otoh, are hardly dangerous. They're not a menace, they're not an eyesore, they don't muck up the neighbourhood - at least, no more than domesticated cats do!
Most cats never go entirely domesticated, they still want to wander the neighbourhood occasionally, they might get into your bins if they're not closed properly, visit the neighbours' houses, kill the odd bird or rat. It's a rare cat that never has the slightest urge to leave the house -and probably a rather unhappy one from my experience! My family have owned cats for the last 25 years and I've had all sorts - couch potatoes who treat the outdoors as a strange and dangerous world, and others who were practically feral, would disappear for days at a time and would give you the most hate-filled, threatening gaze if you tried to keep them indoors. Therefore, the argument that stray cats mess up neighbourhoods is completely fatuous, as they don't do anything domesticated cats don't also do!
Taking in stray cats and putting them in cages seems like a waste of resources. Putting them down after a period of time is particularly cruel and pointless, as those cats would have a perfectly good time as strays, woiuldn't bother anyone and might even help with the rat problem most cities have!