These are my newest MAC brushes and they've quickly become favorites! They're both duo fiber brushes.
The 159 is amazing for highly pigmented blushes- it doesn't pick up too much product, and its easy to both apply and blend with it. I also like to use it with glittery blushes so it doesn't pick up too much of the glitter, but that might not be useful for everyone. I'm going to test it this week with a new cream blush I just bought....I'm thinking it will work great with that too!
The 286 looks kind of average, but the size and shape are just perfect for blending... A little too long and fluffy for crease work for me personally, but it might be workable. I love how it doesn't overblend.