Let me start out by saying that while there is some merit to the "book theory" of higher-frequency detectors being 'hotter' on lower-conductive targets, and low-frequency designs being 'more responsive' on higher-conductive targets, the fact remains that never is this 'science' a rock-solid, absolute, take-it-to-the-bank conclusion.
I've used low-frequency detectors that didn't really do much better on silver coins than other metal targets of similar size, and I've also and disappointing results when using some high-frequency detectors. Personally, I'd take a good performing detector, regardless of the operating frequency, if it showed reasonably good performance on a broad range of commonly sought after target conductivities.
Back in 1998 I set out to find more quantity than quantity, just for fun and a change of pace, and I had a 12,479 coin year. Not nearly as great as 'the good old days", but I managed this goal (I set out to best 10K coins) using a White's XLT, Classic III SL, Classic ID and Tesoro Bandido, Pantera, Bandido II