Here's a general consensus from all the synthetic brush reviews and discussions I've read over the past few months
The Plissson seems to be the front runner in terms of softness, holding water / heat, and splaying the easiest. Some find it floppy feeling though (although they all say it loads hard soap very quickly), and the version sold by Loccitane store has a wood handle has all the normal light-feel and durability problems wood has. The one available directly from Plissson has a high quality synthetic handle (and a much higher price).
The Muhle/EJ STF 2.0 seems to be the front runner in terms of a scrubby tipped feel, good back bone and a good quality handle. Some find it too springy / hard to splay though, and that springiness makes it tend to dump it's water all at once rather than gradually like the Plissson.
Both make outstanding lather, very quickly, with little soap. The Plissson is a little faster, but they are both way faster than badger and boar.
The Grooming Company seems to be the runner-up, and makes the Plissson fibers into a knot that is wider and set lower for a denser feel- but it has a very stubby handle and doesn't splay well. The knot reportedly work great if you reset the knot in a longer handle, and at a higher loft.
Ps: I personally have the Plissson by Loccitane. I face lather with hard soaps exclusively. It's makes such good lather, so fast, with such little soap - that I stopped using my silvertip badger and 1305 boar. And I don't have any concerns about vegan issues, nor any need for the brush to dry fast.
