Normally DD coils will give better performance in heavily mineralised ground conditions.
Mono coils can get a bit more depth if ground conditions are quiet.
A mono on the beach is the way to go, except in heavy black sands.
DD's are a better choice if looking for gold in highly mineralised soils, such as here in Western Australia.
The DD is probably stock as Garrett is aiming the Infinium more towards gold hunters than water hunters (maybe?).
The size is the same, however, the coil windings are different inside.
Tony.
