You cannot replicate a polarizer in Photoshop. GND yes, CPL, no.
Ok? Why? Is it because the informaton on the RAW file is insuffisient, thus not giving you the range to tweak in pp? I thought that you could alter the type of saturation through masking afterwards. If this is right, and I am not suggesting that you and Neuro are wrong, means that I will have to get a CPL for all my lenses, before I take a plunge into Lee.
When you boost saturation in Photoshop, you can introduce noise, artifacts, and other funky undesired effects. If you do it via physical filter, the saturation is real and looks better.I guess its kinda like digital zoom vs optical zoom. If you "zoom" digitally your really just making things worse. The only way to get a good result is to make the modification before the capture.
Also, reducing unwanted reflections increases detail in certain subjects (such as rocks and leaves), that can't be recovered in PP. More than amy other filter, a CPL is the one that can't be replicated in PP. Bear in mind though, that they work best when the light source is at 90 degrees, so if the sun is directly in front or behind, then they will have little or no effect, unless you also have water or other shiny surfaces coming into play. While to some degree, the effects of ND grads can be replicated in PP, that only goes so far, if part of the image is too blown, then no amount of recovery will recover it, so then ND grads also become vital and can't be reporduced. While HDR will recover detail, they often don't look natural, without a lot of care and some scenes (such as those containing high contrast transitions and snow) really don't work with HDR.