What's best for you?
Outdoor and event photographers should consider a high-quality protection filter when working in the field. If most of your work is in the comfy confines of a studio, adding an extra layer of glass shouldn't be necessary.
Polarizing filters are particularly handy for landscape artists. I also like to have one in my camera bag to help me tame reflections when working in contrasty light.
And if you like to shoot at wide apertures for shallow depth of field, or want to slow the shutter for a soft, flowing-water effect, then ND filters are certainly worth the price. Videographers also are big fans of ND filters to help them control depth of field when working in bright conditions. In a pinch, you can use a polarizer to help reduce light to the sensor, since it absorbs two exposure stops too.
Sign up for CIO Asia eNewsletters.