How are elliptical winglets better than blended winglets? I've read in few papers that elliptical winglets give better performance than blended in terms of their L/D ratio. I am not able to find why elliptical winglets are better. the two differ by their profile followed.
Edit 1: Here  are few references
http://ijari.org/CurrentIssue/2017Volume4/IJARI-ME-17-12-148.pdf

http://www.iaeng.org/publication/WCE2015/WCE2015_pp1144-1148.pdf

Edit 2: The papers explain that elliptical winglets are better than blended just through observations from CFD study.But they do not draw conclusions on how it is better and I couldn't understand that from the contours also.
The best way to understand why elliptical winglets may be better than blended winglets is to read the text of the patent obtained by the inventor of the elliptical type, Dr. Fort Felker, a former NASA wind-tunnel researcher and expert in the field of computational fluid dynamics, and co-founder of Winglet Technology LLC.

The short answer is that the curvature of the winglets as they extend outward from the intersection with the wings approximates part of an ellipse (hence their name), and this apparently ensures an elliptical distribution of lift both horizontally and vertically, resulting in lower induced drag than a blended winglet.