The most optimal is to have a top of the dashboard that is not reflective from the factory, or put a flat black dashmat there as a aftermarket solution, and then in 3 place come the CPL which most people still end up with for good reasons.
But a CPL do take a little light, but with the sensors of today that is a very minor issue.
And you do not get a non reflective dash top from any factory, and a dashmat are not the most pretty thing even if designed for the car, but for the down to earth driver it is a good solution.
So most end up with the CPL filter, and they do also take away the most annoying reflections, but really bad ones they can not handle as in make them go away.
Personally as a addict i run both CPL filters and a DIY dashmat as no one make such things for my obscure little red Suzuki car.