PhaseTech said:
the million dollar question is: where will you use it?
Yes - location may play a part. Are you gearing up for a return to oz? If so I'd reckon DD coils would be better options for the the GP series (I'm assuming you got that GP3500?).
Having used a Nugget Finder Advantage mono on the GP3500 in the "fluffy grey soil"
of NSW & finding it still a bit much my own personal opinion is DD's are more user friendly on them.
My take on coils is:
GPX series mainly monos & at least one DD in case you need it
SD/GP series mainly DD's & at least one mono if you find areas you can use it
Reports on the Elite & Evolution mono coils on older machines seem to be mixed at best. I would try one before buying in Australian conditions at least.
I have seen somewhere that the Detech 15" Ultimate DD runs well on the SD/GP's & that would be the one I'd be seriously considering if running a SD/GP here.
Edit: written before I read the above post.