I have not used Nik's noise removal, but do use Topaz's Denoise3...it is very effective and can really remove heavy-duty noise to light fine grain stuff. ; I do like the various controls to adjust the noise removal properties - strength, cleaning, detail restoration, restoration in different color areas, color noise vs base noise, chroma control, etc.
I also still use Helicon noise reduction, which is a very fast and easy one with lumi and chroma controls for when I want speedy results or just need light noise removal from blue skies or something. ; But Topaz Denoise3 is very good.
I bought the package for Topaz, with Adjust, Detail, Denoise, Simplify, Clean, etc. ; Adjust, Denoise, and Detail are really the 3 I use the most.