Another third-party measure of insurers came in a 2012 survey by the Colorado-based Medical Group Management Association, a professional association of medical group administrators and executives. The group claims more than 33,000 members.
In that survey asking administrators about their experience with the payers, Medicare did best, with a score for overall satisfaction of 3.53 out of 5, followed by Cigna (3.20), Aetna (3.16), Coventry (3.00) and United Healthcare (2.77).
Looks like the source you provided is a mixed bag, with a survey that shows Medicare is preferred from a claim perspective (Colorado survey), and others that show they may have had higher claim denials, but the data has lots of variability and is not directly from the insurance companies.
This is an exceedingly simplistic analysis and doesnât take into account substantial differences in the type and characteristics of various patients.