I have a Simpson that I use for creams mostly, it is a great brush. I can not comment on Thater though as I do not have one (at this current time).

My go to brush of the 3 I own is one that "pixelfixed" made. I can without a doubt say that if you get a brush from him that you will use it often. I also have to comment on his willingness to make sure things are right. He was not happy with the way the first knot was and informed me that he had ordered a new knot for it. He clearly stands behind his product and is willing to ensure that everything is is in tip top shape.

Keep in mind that you may want 2 good brushes at the minimum if you use both soaps and creams. I like the softer brushes for the cream and one with a bit more bite (stiffness) for the soaps.