Some of the cheaper Plisson brush handles are not of high quality.
I bought the brush linked below and the handle is hollow plastic, very tacky.. like something you'd get with a 'Made in Taiwan' toy gun from the pound shop.
http://blaireauxplisson.com/en/shavingbrushes-fiber/257-blaireau-facettes-loupe-de-noyer-blanc-europeen.html
I have a fairly decent collection of synthetic brushes (Kent, Omega, Plisson, Simpson x 2 & Muhle V2 in an EJ handle) and my pick of the bunch is the Muhle V2 as I just find it is well balance for my preference - soft tips, a nice amount of backbone, not too springy, splays nicely.
The Plisson knot is highly regarded by many, but for me it's too soft and just doesn't give me the amount of back bone I prefer in a brush. The Kent and Simpson knots are very springy in my opinion. The Omega is a tad to firm and scrubby for me.
All the synthetics I own lather soaps very well. It then all boils down to the style of knot you prefer.