Castrated male kids - no milk, no agression, no smell (and no issues with them trying to find girls either - usually) and produce quality meat. Once you are ready to milk, get females then.
Look into horned vs disbudded, and then stick with whatever your choice.
GG's - laid back, easy to handle, nice milk but only "household" quantities.
AN's - somewhat less laid back, not quite as easy to handle, but super quality milk (high butterfats) and more than GG's usually. But easier to get hold of than GG's.