The Nox is a simultaneous multi frequency and selectable single frequency detector that is supposed to be fully waterproof (there have been many reports of leakage lately but the warranty covers it). It is much lighter than the Etrac with similar audio tones and audio adjustments, much faster recovery speed, better target separation and excellent depth even in mineralized soil. It has very accurate target ID after getting familiar with it but it isn't as good as the Etrac's incredible accuracy. I really like the display and features. It is very good to excellent at every detecting scenario you can think of except maybe submerged in moderate surf conditions and hunting relics in thick iron trash.
The ORX for about the same price as the Nox 600 and cheaper than the Nox 800 is an interesting comparison. Personally, the ergonomics of the ORX/Deus are unbeatable along with the overall recovery speed and target separation of these detectors. The Orx has 21 (I think) one at a time, selectable frequencies depending on which coil comes with it. It is limited to 3 tones maximum in the two discrimination Coin modes. The Gold modes are good for prospecting, relic hunting and dry sand beach hunting since they are true threshold based all metal modes with an Iron Audio Reject feature that helps tone down iron audio responses. A big minus is that the moment you submerge the coil in water you will lose contact with the coil's wireless connection unless you buy the underwater kit. So, if you are primarily a relic hunter or detect in areas that are not target rich with lots of aluminum trash, the ORX would be an outstanding choice. If you are looking for a detector that can do everything very well like the Equinox, I would not consider the ORX to be in that category. The audio is somewhat limited adjustment wise and is radically different but full of information when compared to the mellow and somewhat less informative tones and many tone options of the Etrac and Equinox. Also, even though the target ID screen is much bigger on the ORX than the Deus, the numerical target ID function of the Deus and ORX is one of their weakest features since accuracy on deeper targets or targets in high mineralization is very iffy or non-existent and the Deus and ORX become tone only detectors past about 4" in my area in high mineralization. So, the Orx and Deus are unmatched at relic hunting away from lots of modern trash, they are good gold prospecting detectors and can handle some beach conditions. As a day to day modern trash park hunter..............the ORX would be okay for surface to shallow targets if you don't mind wading through lots of trash and depending on what coil you buy.
If you had the money to get both, they would compliment each other very well!!!
Jeff