I like them because I can get the target separation of a small coil while getting the ground coverage of a larger coil
Plus, once you understand them then you know how much ground you are covering per sweep at a certain depth range.
In the air, the footprint of a concentric coil is more bowl shaped than conical. But in the ground, the ground minerals condense the footprint into a more conical shape. The higher the ground minerals, the more narrow the conical footprint.
For example in a certain soil with an 8" concentric, your coil foot print at 6" might only be 2" wide. That means if you are looking for 6" deep coins and you really want to cover the ground you have to focus on making sure you get a good 80% coil overlap, otherwise you are missing a lot of ground at the 6" depth mark.
The widescan coil footprint is long and narrow. The soil mineralization affects it the same way, squeezing the footprint, but without as much affect. So in the same soil of the example, with an 8" widescan coil, I would be getting a 5" long, but maybe only a 1/2" wide footprint. That means I only have to overlap the coil by 40% to achieve the same type of coverage at depth. That is much more forgiving than 80%.
The narrow width of the footprint separates targets like a knife. So even in high trash you are separating alot of targets just because the field is so narrow.
So I like the widescans because I have to pay less attention to coil overlap and get great separation. The machine also sees less of the ground minerals so in higher mineralization, there is a lessened affect of them.
Not to forget pinpointing. With a widescan coil you don't have to x the shallower targets, you can just poke the coil at them and let the VCO tell you were they are. or do the DD wiggle, and pull the coil back away from the target as you wiggle the coil back and fourth until the audio is gone, then move the coil back until the signal returns and the target will be right under the toe. Or further back depending upon depth. Once you learn the coil and the soil you hunt, it gets fast and easy.
I just love them for the modern (1950+) sites I hunt as most of the stuff is still inside the 0-7" range.