My favorite is 168. I really like it because it does all the work for you. The cut of the brush (angled) makes the application effortless. With this brush, when you blend towards your hairline, it tapers off perfectly.
I guess I'm the oddball here. I like the 129 because it's more dense, picks up more color, & is smaller for precise application. Don't get me wrong, the 187 is my favorite brush of all time, but I prefer "the killer" (click here for reference) for sheer application.
Thanks so much ladies for all the great suggestions. I did go with the 187 brush & tried it for the first time today & I LOVE it! It's buffs in my blush & makes it look so beautiful & natural with no harsh lines which is the problem that I was having with my old blush brush. I also love that nomatter how matte or bright a blush is, this applies just the right amount so you don't look clown like, but can keep going back & adding more color until you get just the right look. This is my new favorite brush & I am sooooo glad that you all suggested it to me, it's exactly what I was looking for ; )