The coils are more noisey, both the Elite and the Evolution, the reason being is that both coils by the nature of their design have more wire turns in close proximity to the ground, thus more ground noise if the ground is reactive.
The coils are (in my humble opinion) an attempt at getting small surface gold while trying to maintain some depth.
So are they are they good coils? yes but i would be wary of using them for deep targets in noisey ground as the signal to noise ratio is trashed. Just remember that there is no such thing as a free lunch when it comes to coils, where you gain on something you will lose somewhere else. So is you are after depth on reactive ground use a smaller mono or a DD, to this day i still have not seen a world class DD coil but i have not looked inside a dtech coil yet.
You know who makes the best coils? lol I have some very good coils, pity they are not sold in shops.