1} General park/school ground type turf hunting, (moderate target/trash density)
Most parks I hunt are super trashy so snipers are my favorite.
The 5" Fisher coil worked great but I eventually switched to a Sharpshooter and just use that now.
Works as well or better than the Fisher and is shielded better so quieter and more stable.
2} Heavy modern trash
Same deal...snipers.
3} Iron littered old sites
Repetitive but again....snipers.
I actually learned to hunt in heavy iron using the 11" DD Fisher coil too but using small coils are much more efficient.
4} Field/Relic hunting
Bigger coils, 11" DD but I also have and use a larger Cors Cannon coil.
5} Deep targets
The bigger coils, but snipers on these things can get way deeper than you might think depending on ground cinditions.
If they were deep targets but hiding in sites with a ton of iron or trash I probably would still go with the Sharpshooter.
Let me add one...
6} Jewelry hunting
If I am seriously looking for jewelry I often go straight to the 10" Elliptical concentric.
Most F75 owners don't add this one to their arsenal and most F70 owners that got this one new were told to upgrade to the 11" DD...and they did.
There is a difference in the tones between this one and a DD when it comes to swinging over precious metals...the concentric is not only a different sound but it is sweeter, for lack of a better descriptor.
It goes plenty deep, works great in heavy iron and trash, too.