Julie,
I agree about show cats -- I just don't know enough to even attempt it. Plus, cats are just plain harder to shoot. I really appreciate the work of Preston and Tori who seem to have a real affinity for and with cats. I love them, but I don't really know anything about them conformationally.
As for breeds of dogs, I have difficulty with the rare breeds because I seldom shoot them in a show setting. I really don't know their Standards as well as I should and I don't see images of them as often as AKC breeds so there is little to compare in terms of angles, perspectives, point of view, etc. I've shot Specialties for most of the AKC Breeds and have a pretty good working knowledge of how they should all be set up. But, ultimately, you are at the mercy of the person holding the lead and whether or not they can stack the dog properly. Owner/handlers are the worst (and I am one so I can say that). They feel that if a breed is only to be free-stacked in the ring -- Collies for example -- then that's the way they should be set up for the formal photo. Fact is, every dog should be able to be hand-stacked just so you can position them properly for the show formal. Professional handlers can do both.
The other element in shooting show formals is the time limit. You only have a few minutes to get the image and everybody's in a hurry: the judge wants to get out of there or onto the next breed; the handlers have other rings to make; the dog has just showed and has just shut down from "show mode". I ripped through all the show shots from each Specialty in less than 15 minutes total. And that includes getting my share of puppy kisses

. You have to be ready so that when the dog is stacked properly, you are prepared to toss the toy and get the shot.
As I've said, I don't know why people want to do this job. Must have something to do with masochistic tendencies

.
Jim