I'm not sure about it but here's my guess: The Jepp routes are
"preferred routes" put together by ATC that take into account traffic
flows. DUAT, however, is independent of ATC and makes up some
reasonable route, where "reasonable" was decided by the people who
wrote the comptuer algorithm that comes up with routes.

Andrew Gideon wrote:
Planning a flight from CDW to CQX, I found in Jepp one route: BREZY V39
CMK V3 HFD V167 PVD V151 GAILS.

DUAT offers another: FALLZ V3 JEWIT V167 PEAKE

Am I likely to get the DUAL routing if I request it? I'm surprised that
it would yield something different from Jepp. Admittedly, it's not
much different but at the ends. And the Jepp route would be easier to
enter into a GNS 430 (though the DUAT route would be easy for the 480).

But why any difference?

- Andrew