I don't know the science behind all the stuff. To me, either it works or it doesn't. Either it kills the noise or it doesn't. The problem with the NS-2 in comparison is that it cuts off sustain. Nothing like throwing a little wiggle on a note to have it cut off. True, you can adjust the NS-2 to cut off later (or earlier) but then it doesn't handle the noise/hiss as well. The ISP will cut off sustain if you dial it in on a very extreme setting but it will always cut off the noise.. I run my proper tour rig which is a two amp set up and I can have it set to stadium level volume and stand right in front of my 4x12's and shake my guitar with strings un-muted and it is silent. I can then hit a note and hold it and let it ring out and it just rings. True, the rack units are probably better than the pedals (they should be, they cost much more) but I use the pedals all the time and have similar results. Granted, I don't usually play at insane volumes when using the ISP pedals but the result is the same...no noise, and that is all I care about. Out of all the pedals ISP makes, my favorite is still the original one. The decimate baby pedals work ok but have a bit of attenuation to them in certain settings. I happened to like that if I am playing at home late at night and can benefit from some volume control. It is very minimal but in a very quiet situation it is a positive effect or attribute IMO. The G-string is nice as well. I already had a few regular ISP pedals when it came out so when I got it I didn't really see any benefit other than amount of pedals used (which could be huge to some folks) it wasn't so much to me.
No matter which ISP product you choose, It will solve the noise problem. Hopefully my storybook here helped rather than confuse. There are other products out there that I am sure good. I just have the most experience with ISP. I know Fortin makes a gate that is a knockoff (basically everything Fortin does is a knock off of something) of the Kerry King Marshall signature amp. People I know like that product but it is overpriced for what it is and I am not a fan of Fortin.