Let me put it this way, with a true example of the merits of TID machines:
A friend and I were hunting a furroughed ag. field area, where an assimilitation/contact period indian rancheria had been. The site turns up reales, buttons, relics, etc.... Since it is a "relicky" site, we both hunt it with a "relic mindset". Ie.: "dig all" (with the exception of iron). He was using a 6000 Di pro with meter ID, and I was using an Explorer with tone-ID. As it turns out, we would hunt this spot at night (because of our work schedules), so his 6000 di pro screen was hard to see. But he didn't care, since we were in an "dig all" frame of mind. And I too would dig all signals, even in-spite of the tone ID on the Explorer.
However, night after night, I would always spank him 3 to 1 on coins and buttons. Like if I got 3 coins and 3 buttons, he'd only have 1 each, etc... But when we would go to count our "woulda-couldas" (junk, aluminum, period green copper slag, doohickeys, etc...), our counts would be almost the same. Why then was I constantly getting coins and buttons in higher quantities? At first he mused that I must be "cherry picking", because of my tone ID (which his 6000 lacked). I assured him that I was not purposefully cherry picking, and I simply didn't know why I was spanking him. Depth was not the issue, since it was a plowed field, and since our target counts were approximately the same.
Finally I/we figured out why the explorer was spanking him: Because the field was SO prolific with targets to choose from, my mind must've been subconsciously passing the flittier junky sounds, in favor of the "round" clean sounds. It wasn't on purpose mind you, since I was in "relic mindset". It was totally subconscious, because with oodles of targets to choose from, the mind will gravitate to the sweeter sounding ones, and pass the can-slaw thin whispy non-round sounding ones. I suppose the 6000 Di pro guy could do the same thing, if he was watching the screen and the way the needles bounces, but the tone ID just made it easier and instaneous.
You can guess that by the 4th or 5th such spanking, he immediately went out and got an Explorer

This is just one type hunting though, so this type benefit of TID may not apply in a lot of other situations.