Boeing claims a 0.5 - 0.7 EPNdB noise reduction with its blended winglets.
. Given that the human ear can distinguish down to a 1 dB difference in sound intensity, this benefit is marginal at best. However, Boeing states that:
“At noise restrictive John Wayne airport in California, installation of blended winglets would take a Next Generation Boeing 737 from a category A to category AA
. This could mean an additional 39 flights a day, which is extremely significant. "
This is probably a special case in which the standard 737 sits right at the edge of a noise category. I doubt a 0.5 EPNdB gain would result in any operational advantage at most airports.
The winglets also add about 480 pounds to the plane's empty weight, which is why short-haul operators do not seem eager to add them. The fuel savings claim for long-haul 737 flights is 3.5 - 4%.
Keynes is dead and we are living in his long run.