Short story....Zuul wins over G string. Longer story..... The Zuul has a faster clamping action for chug, stacatto etc. And that's saying something because the Decimator G String was very good. The threshold knob can be set much lower on the Zuul for the gating effect. This leaves a better sustain as well. I've read a few statements that the Zuul is just for fast, choppy gating. Not true. It is very transparent, as good or better than ISP and it absolutely can be set to allow for long sustained notes. I find no artifacts, tone loss etc from the Zuul. It powers back on again when you remove the power supply, whereas the ISP did not and you had to press the pedal again. Small issue, but better for my rig as I want it to stay on when I power back up. Zuul seems more forgiving with the 3 cables vs 4 needed for the ISP regarding ground loop hum as well. Again, more so a specific rig set up issue. I have the knob set at about 9 to 10 o'clock for dead silence with very high gain amp and overdrive. The ISP needed about 1 PM to achieve similar. Sensitivity for the Zuul key in seems more smooth. The ISP could be on the edge, like it wasn't sure whether to gate or not and you could get an in between problematic area of the gate opening but with some artifacts. The Zuul is much smoother in this regard with either tight clamping or a smoother opening at lower settings. The Zuul was shipped with a new Duracel 9 volt battery inside. Comes with a few cool Fortin stickers and the little stick on foot pads for the bottom of the pedal. Zuul has the colored LED's for gate action which is another small bonus over ISP. For practical reasons vs cosmetic, the LED is slightly slower to respond than the actual gate action. (milliseconds, but noticeable if you are trying for a visual cue etc) Considering they are both about the exact same price (darn high) I would recommend the Zuul for new buyers and a slight improvement over the ISP for current G string owners. I am happy I've made the upgrade. I live approx 60 to 90 minutes away from Mike Fortin headquarters in Canada. However, the pedal shipped from Kentucky USA? It took about 5 business days to arrive, but was very inexpensive shipping cost and no duty issues right to my door. I hope this helps others with the decision and interest between these 2 great noise reduction options.