People in general like to jump on the new machine bandwaggon and there as been tons of pushing especially by people who test the new machines that are also given those machines for free so with that comes a bias about the machine. This isn't just SMF's but we see it in the prospecting world even with PI's.

I had beta tested equipment and software for over 30 years and never promoted the products I tested. In turn for my efforts I was given the products and updates. My unbiased feedback helped make the products better as there was no incentive otherwise.

I have used both SMF and SF and really depends on the grounds your hunting, how well you know those grounds and the targets you suspect in finding. Old properties that have iron infestation the concentric coil on an analog machine still work best. Areas with modern trash modern machines with small coils work better as you can filter out or recognize the trash better.

Machines with modulated audio INCLUDING modulated iron audio help quite a bit as you can determine size and depth of targets OR true all metal that does not lock onto targets and can mix targets into a signal such as prospecting machines.

Majority of grounds SMF and SF machines will do just fine and find targets more likely due to the user putting a coil over it and digging than the actual frequency/frequencies used.

As for sensitivity, the Tejon with a small coil can pick up small gold almost as good as a Gold Racer. One is 17.5khz and other is 56khz. Reason is about coil design and where the machine determines what is ground and what is a target and how finite that target range is to the mineralization range.

Good example on machines that have a low response to minerals and boarderline iron targets is the Cibola, Vaquero and Orx with 9"HF. All of which I have used. The Orx will actually only give a ground phase respons on targets as large as rusty tinned cans and will mask out targets around it because of the DD coil and low response. Cibola and Vaquero with concentric coil will manage to squeak out a peep at least but will also fail with a DD coil.

There is too much hype about the machines as it has been for as long as I can remember and I just stick to what I know and what works. I often hunt with a buddy who has an Apex and now a Vaquero and I will use a different machine so we can cross check targets.