Stating that, it does come down to how much the dry sand is mineralized and how much salt content. A unit that can ground balance is essential. Fixed GB units will work, but there may be times when you do need the ability to ground balance.
Here in NJ in the dry sand, most any VLF ( both multi and single frequency units) work well.
There are lots of great VLF choices out there....as always it depends on how much you want to spend, what features you want, and what you are comforable using.
Hard to recommend just one VLF unit for dry sanding, unless you specifically want to sniff out gold versus old coins/clad. What would be your main target choice ?
One of the cool things about the Deus and Minelab 705/505 series (as well as other units) is you can change the frequency.....so if you want to have an advantage for lower conductive targets, use the higher frequencies, where as hunting for old silver, use the lower. These units can also mitigate being hot on surface foil and aluminum because you can utilize a lower frequency when you hit the areas where there is an abundacne of that type of trash. The unit will be less 'reactive' to those types of targets and can discriminate a bit better.
These 2 units ( along with others like the DFX, V3i ,etc.) where you can alter the frequency you are hunting in, give you more options when conditions change, or when your strategy changes.
JMO