Marie, you mentioned PLM's. The problem with the large ones is the eyeshine that Ty mentioned. The light source is so large that it is hard to pose the head of the cat at an angle that eliminates the discoloration. Unless you have placed them 20 or 30 feet from the subject. Then you don't really get the wrapping of the light from a large source.

With cats, the size of the light source, the distance from the subject, and the position of the light relative to the lens axis all figures into the result. Bigger is not necessarily better, closer is not necessarily better or worse, its a combination of it all.

Regarding umbrellas, my nit with them is seeing the spines of the umbrella in the catchlight. To me round or square looks natural, but 'flying saucers' do not.