I use both the NS-2 and NS-1X with the amp’s preamp in their loop. Guitar to NS input, NS Send to amp’s input, amp’s effects loop Send to NS Return, NS Output to amp’s effects loop Return.
If you’re also experimenting between the two, notice that the jacks are flipped between the two pedals. If you’re not paying attention you’ll plug into the wrong jacks.
(Those are my actual settings)
As expected the effect of the noise reduction is similar between the two. However, you get much better control with the Damp, the Threshold seems to have more range and the Decay seems quicker. Plus you get to choose between Gate and Reduction. Also the Mute mode allows you to switch between Gate and Reduction with a long press of the pedal. The LED display is kind of a big deal here as well. For setting and monitoring the noise reduction, it’s very useful. The Decay setting is more important and a bit harder to dial in on the NS-2. I think that’s because it lacks the Damp control.
If you’re happy with the NS-2, I wouldn’t run out to get an NS-1X unless you really need a Gate function but it does have some important improvements in the controls. I don’t think you’ll regret spending the money, I don’t. However, I also don’t think you need to immediately replace your NS-2.
If you’re buying your first noise reduction pedal or need another for a second pedalboard, definitely go NS-1X though.