I consider the Equinox and Deus as sophisticated Beep and dig digital machines that just happen to have visual ID assist. Beside the reliability and straight ahead analog functionality of the Tesoros, their circuit simplicity and minimal filtering enables them to be killer fast in recovery speed.
It has taken some significantly sophisticated digital processing horsepower for the likes of ML and XP to emulate that fast and nuanced audio aspect of the Tesoros in a digital machine while enabling the advanced discrimination capabilities, and in the case of the Equinox, the versatility to handle a wide variety of detecting situations via the multi frequency and signal processing wizardry of Multi IQ.
Agree there is something to be said for having a beep dig as a backup, but it takes a lot of patience and swing hours to really learn the audio language whether it be a Tesoro or Equinox. If one is used to visual ID (especially the more sophisticated visuals or IDs associated with the "high end" Minelab CTX's and eTracs, and Explorers as described by Charles or the high end Whites machines) as the primary means of detection with fewer audio tones used, then it is harder to get used to 50 tone audio or Full tone audio ID, especially if you have visual ID to fall back on.
Audio doesn't always have to be sophisticated though and less is sometimes more as far as audio is concerned and detecting success, but that also requires more reliance on visualmID. Two-tone is a great iron unmasking tool but requires Visual ID assist if you don't want to dig it all. Similarly, the VCO pitch like audio with true threshold will really ferret out small or deep whisper keepers, but again visual ID is a must if you want to make dig decisions.
That is not to say that primarily visual ID machines can't get it done. That is obviously not true. And there are some pretty sophisticated visual interfaces that are very powerful tools. I think seamlessly marrying both sophisticated audio with decent and reliable visual ID are a killer combo.
That being said, though I personally tend to over focus on technology and the machine (which is natural in the brand forums) because I enjoy talking about it, I think here are few absolutes or simple answers in detecting success, suffice to say that detecting experience, patience, perseverence, familiarity with your machine, research, and probably most importantly, site selection all tend to trump technology alone, in my opinion. Put me out in a field with the most sophisticated detector in the world, even if I know how to use it, and the experienced detectorists I know here and elsewhere like Smokey, Calabash, Terry, Charles, and a host of others will mop me off the floor even if they are just swinging a broom handle with a pinpointer stuck to the end of it. Lol.