That doesn't address the true advantage of the crop factor though. It
would demonstrate the telephoto cost, weight, usability advantages,
if you used a 200mm f/2.8 vs 300mm f/2.8 comparison. The d3 system
would be heavier, less portable/usable and significantly more
expensive.
Ah, but that's not a valid comparison. To truly achieve the closest
image possible on a DX camera as an FX camera would with a 300/2.8,
you'd need a 200/2 on the DX camera. Problem is, the 200/2 is the
same weight, only 2 inches shorter and only $500 cheaper, so there's
not much of an advantage there at all. This takes us back to the
issue of qualifiers. "Better" is meaningless without a qualifier.
To you, perhaps the 200/2.8 is the DX equivalent of a 300/2.8 on FX.
But it's not. And just because you say "I don't need the same DoF"
doesn't mean no one else does either. Now if there actually WAS a
DX-only 200/2, then we might have something, but the list of pro DX
lenses is about 1 lens long (17-55), and I don't have much confidence
that that will be changing.