A good dense synthetic brush must comes with a perfect balance loft height, backbone and splay. When the loft is too short it's becomes very springy and doesn't splay very well the backbone is too strong, if the loft height is too long becomes very floppy and it's splay too quickly and looses it's backbone.
It's not very easy to find the perfect dense synthetic brush straight away, because you have to buy them until you've find out the perfect synthetic brush as YMMV.
I have two perfect synthetic brush for face and bowl lathering in my den which are:-
The RazoRock Plissoft (Bruce handle) 24/57mm knot and the Edward Jagger (EJ28) v2.0 Silvertip Fibre in Faux Horn handle 25/58mm knot.
I'm pretty sure the RazoRock Plissoft Beehive handle 28/57mm knot would be excellent as well, I haven't tried it yet.