I am curious why you would ask this question? From the examples you offer, only one person posted a comment on youtube saying it was because he owned both brands and now has the NAD.
If that is the case, then Parasound is better than NAD. Why? Because I now own Parasound when I use to have NAD and I say it is.
See how ridiculous some anonymous youtube comment is. See how ridiculous my comment is.
Marantz PM15S2 LE, Arcam FMJ CD-17, VPI Traveler V2 with an Ortofon Rondo Blue, Technics SL-1400 with an Audio Technica AT-14sa, Simaudio Moon 110LP, Pro-ject Phono Box S, Pioneer Elite VSX-52, Pioneer Elite BDP-52FD, Dynaudio Focus 260's, Vienna Acoustics Theatro Grand, Wharfedale Diamond 9.2s, REL T-1 & Panasonic TC-P54S1