It is pretty obvious that these brushes aren't dupes, but they're still a similar concept that warrants some comparison since buying one over the other could save you THIRTY-TWO FREAKING DOLLARS.
Duo fibre brushes have a lot of applications (heh... pun) in the makeup world and can do just about everything on the face from "airbrushing" foundation to applying highlighter to applying cream or powder blushes... hell, if you're feeling really creative, they can create some really nifty effects on nails. I personally prefer to use them for applying cream and powder blush since I can be a little heavy handed and it gives them a nice, diffused and natural look.
Now that we're on the same page about duo fibre brushes, let's get into the deets surrounding these two suckers.
I honestly, and unashamedly, chose the dinky little $3 e.l.f brush over the overpriced - and frankly quite bad - MAC 188. I just don't find that the MAC one has enough surface area and is too bendy, courtesy of the longer white hairs. One other major fault with the MAC brush is that it sheds like none other. I've had it for about 3 years now and I still find the odd hair stuck to my face or in the sink whenever I use and wash it.
Save yourself the money and go for the cheaper option, folks!