I use the 129 and the 187. The 129 is primarily blush and could be used with loose powders to highlight or to apply bronzer. The 187 gives more of an airbrushed look, PLUS you can use this brush for MSFs, liquid and powder foundation.
I use the 187 for blush most of the time so rec this or the 188. I find its really easy to control how much blush is being applied because it only picks up a little bit of product at a time due to the bristles. So, you can lightly sweep it over the cheeks or continue to apply and build up the colour. As mentioned above, this brush is pretty versitile in that it can be used for foundation too
187 is awesome because I get the fool proof flushed look when I use it. Blends it it very well and softens the edges so it looks airbrushed.
The brush has so many great uses. After I put my liquid foundation on I use it to buff it out to soften it. I use it for my MSFs. It is the best invested I have gotten. (Thank you specktra for your reviews!)