Last sentence from A wiki entry on the Davis wing.
"As speeds of aircraft of all sorts increased, the Davis wing's low low-speed drag could not make up for its higher high-speed drag, and use effectively ended."
Drag is not simple and what works well at low speed may not work at high speed ( Hawker Hurricane and Typhoon?)
where the crossover point for the Davis wing is I don't know. Davis wings are also pretty high aspect ratio. some good comes from this and somethings not so good.