I have the CS Silver Duo Fiber Stippling Brush & the MAC 187. Naturally, the MAC is a top-notch quality product. That said, the CS brush handle is approx. 2" longer than MAC's & while I find the brush to be as dense as MAC's, it bristles are slightly softer & it's slightly larger in circumference/diameter. Unlike other CS reviewers, I haven't had a problem w/ shedding. For the price, I very much like this brush, but it can't hurt to check out the Studio Tools & the Sonja Kashuk Duo Fiber Brushes @ Target. Unfortunately, some Targets never seem to carry the highly popular SK Stippling Brush. I've, also, heard alot of good things about the sigmamakeup SS187 & SS188 MAC dupe brushes which are only $16 & $14, respectively. Youtube has a lot of reviews for all the above mentioned brushes. If I did not have the CS brush, I would repurchase.
I use the CS brush for blush, face highlighting & powder, but I have not used it for liquid foundation. It won't be as seamless in application as the MAC because the bristles are softer, but it will do the job. It is definitely too large for contouring; even the 187 is too large, need the size of the 188.
A duo-fiber stippling brush that's excellent for contouring is Aromaleigh's silk fiber blush brush. This is the brush I use as I like my contouring to be very subtle & this gives me great control over the amount of product applied. It also makes a wonderful highlighting brush especially for the upper cheekbones. Just has all-around versatility.
HTH some.