The effect is remarkable! It's tiny but so present! Good A/B-ing
FWIW I always swith it on first. I even leave it on when designing sounds or while tracking or whatever. It's on by default, nothing else is.
I had a play with the NLS a while back and that sounded to me like it added quite a lot of effect to the sound when cranked up. I may be wrong tho. But I don't want to hear the console, just feel it!