Hi, these brushes are very different. From end to end they are actually about the same length. However everything else is different:
189 - has rounded bristles which are 4cm at the longest point.
- has thick full bristles.
- this is a face brush to be used with powders and blushes.
MAC description - A uniquely shaped, rounded-paddle Face Brush with chiselled edges on each side for effortless placement and precise blending of product. An ideal tool for use in sculpting the face. Very soft synthetic bristles make it perfect for use on sensitive skins. May be used to apply all M·A·C Mineralize Skinfinish powders, M·A·C Powders, Cream Blush and Cream Colour Base.
190 - has rounded bristles which are just under 3cm at the longest point.
- has tapered bristles.
- this is a foundation brush.
MAC description - Pro-quality. A foundation brush designed to create even finish, flawless look. Works well with any M·A·C foundation, including Studio Fix and Studio Tech. . A professional-class foundation brush designed to provide a smooth, even finish, flawless look. Use to apply, distribute, and blend foundation into all areas in the face.
I actually have both of them so I will try to post a picture so you can see them side by side...as soon as I can get my camera working!!