I can only speculate on a limitation: I am not really sure if an optical pen would be pressure sensitive. Which I consider one of the important features of my Wacom pen. Drawing hair is hard without pressure handling brush size and opacity. A Wacom limitation I encounter (on my Mac): I use my pen for everything. Except within Poser (and Carrrara) that can's handle the pressure. I think. Little movements create grossly deformed limbs.