Chemical castration works for only a few days. Then it wears off. You'd have to continuously dose all the strays. A bullet, however, you only need to use once.
True. That's why you use surgical methods. My main problem is allowing residents a liscense to just start shooting. If the ferals are as big a problem as they claim (and, let's face it, feral cats do quite a bit of hunting,) then why not use humane methods? They should also make neutering pets mandatory, otherwise they'll just keep breeding.