Dew --
Yep, on a beach, where you are "digging essentially all non-ferrous," is an example of a time where it could make sense to me, to hunt with a setup using two, or just a few, tones. Some specific relic hunts might be the same way, also. In my mind, it's all about how much digging you intend to do (which has to do of course with what targets you are seeking). If you are generally "selective" about what you are going to dig (i.e. in a park hunting for coins, where lots of modern trash and iron abounds), Minelab's multi-tone setups give you lots of information, once you learn the language and "dialect." In my mind, you'd be shooting yourself in the foot to hunt two-tone. Meanwhile, if you plan to "dig it all," or "dig all but iron," like when gold-hunting on a beach, then the extra tones may prove to be no more than superfluous noise.
Steve