Video wise, Viewty has smoother feeling to the recorded video, while N82/N95 has some ghosting effect like old LCD screens, probably N93 too.

Audio wise, Viewty has no boosting to the audio, probably no compression too so it might distort badly when there's high sound pressure level (means high sound volume), while N82/N95 has compressor, and will not distort easily. N93 is probably the best due to the proper stereo speaker, according to gsmarena, it seems don't have compressor too so will distort badly when there's high sound pressure level.

120fps is a plus for Viewty, but won't have much use in low light condition due to very fast fps, each frame won't capture much light sources.