I only bought 4 brushes, 3 eye blending ones and the cult fave Kabuki face one. The face one was a gift, so that I cannot review.
In my brush collection, I have options, which I love. However, I find myself using my Sigma's over my Mac ones. The Sigma brushes are much softer, have more bristles and I find I have less fallout when I use them vs. the Mac ones. I should do one eye with Sigma's and the other with Mac's.
Also, have you ever had a Mac brush, where the bristles just break? It starts to look ratty and you have a hard time achieving what look you want because the shape of the brush is now a little different.
You can see here how the bristles just look worn.
This has absolutely happened to me, and that is one of the reasons I tried Sigma. I feel like they are stronger than Mac, yet feel softer on the skin.
Similar Mac and Sigma Brush