I vaguely recall this issue back in the very early 1990s. The original Eagle incarnations had the old "buoyant" type white coils. But the latter Eagle II SL was using the 950 loops. Much better incarnation. And in the in-between time, Whites offered some sort of chip, to those with the earlier generation, that fixed some of the wimpy-ness of the first Eagle. Whether or not that allowed the user to also use the 2nd generation loops or not, I don't recall. I recall someone saying they wouldn't ground balance properly. So perhaps you might do well in an air-test, yet suffer in actual ground ? I dunno.
I love my Whites Eagle II SL. But it started to get whooped depth-wise by other machines. CZ6 was deeper (albeit with a few drawbacks). And when the Explorers came out, they too spanked the Eagle II SL as well. If it hadn't been for the depth issue, the Eagle was, in all other ways, a great machine. Not too good on wet salt beaches though. Couldn't track fast enough. Even though it supposedly had auto-track for that, yet it never worked as well as other Whites , like the 6000 Di pro, for instance, on wet salt beach.