You're not alone. I've always felt that there was something odd occurring when using Traktor HID with my original NXS. There always seemed to be something sucking the life out of the track's dynamics, even with the headroom/limiter settings disengaged in Traktor disengage. It could be a placebo, but I can't help but agree with you–though I have no hard proof. If I feel motivated one day, I'll attempt to make a recording using each app and will see if I can spot any differences using my meters in Ozone.
Cheers.