And the winner is......

[fancontroller]

Very nice pic. Which one do you find softer ?

When the knots are dry I can feel that the tips of the Plisson are a little softer than the Whipped Dog's and when in use the Plisson does feel softer against the skin but that's mainly due to the fact that the Plisson has almost no backbone. The WD, having more backbone, feels firmer and has more "scrub" but still has the softness of the tips so I don't know if I could tell the difference between the tips alone in use.

I rate the WD as more of an all-rounder because, being stiffer, it's easier to load from a hard soap and easier to bowl lather. I tend to use my Plisson with creams as the lack of backbone isn't so much of an issue for loading and lathering.
Face lathering is different - the Plisson is so soft that you could face lather 'till the cows come home and not over-scrub your face. The WD is a more efficient face-latherer; more like your average brush, albeit still very soft on the skin.

I showed a top-down photo of the knots in my Acquisitions thread and again shown below (WD left, Plisson right) where you can see the difference in density which I believe is the overriding difference between the two knots.

 

[fancontroller]

...and while on the synthetic subject I've found that Muhle's HJM synthetic brush is also a very capable brush, easily available and at a very low cost, less than £15. It doesn't have Plisson-soft tips but compensates with a firmer backbone but still splays nicely. I use mine for travelling as it's about as indestructible as you can get and delivers way over its price point. At the risk of upsetting traditional shaving brush handle aficionados I'd say it is a great design - solid, very comfortable, rubberised thumb grip and just fits into your hand nicely.
An often overlooked brush IMO.

 

[riverrun]

At the risk of upsetting traditional shaving brush handle aficionados I'd say it is a great design - solid, very comfortable, rubberised thumb grip and just fits into your hand nicely.

I've always liked the look of those hjm brushes. But then again, I'm not your "traditional shaving brush handle aficionado". One of my favourite brushes is this Omega synthetic, which I won in the June raffle:

I think it is very pretty