forgot to say, with my tattooing, the purebreds/registered animals get the full tattoo, which has the herd ID and individual ID, partly because its a requirement for registering them, and partly because its easier to tell who is who if the tag is lost.
With my commercial unreg females, the ones I am going to retain as breeders also get the full tattoo, just because I like to keep track of individual records, and so its a permanent form of id if the tag is lost.
But, with the commercial females to be sold on as breeders, and the males and females which are headed for slaughter, I just give them a quick tattoo with the herd ID only. Reason being, tattoo is a permanent ID form which shows that those animals are MINE. If they get out, or heaven forbid are stolen, and someone is trying to claim them as their own, well its pretty easy to cut an ear tag out and replace it, but you cant get rid of the tattoo unless you cut their ear off (and thats pretty obvious).