Brandon-Hall just released a comparison study of 89 authoring tools for e-learning. http://www.brandonhall.com/public/publications/atkb/index.htm
These do not include Moodle, WebCT or BB--I suppose because an LMS is a different category. Cost of the study is US$795. I do not plan to order it, but it looks comprehensive and presumably neutral third-party analysis. Also note that "authoring tools" are less important in facilitated environments (such as Moodle) where socio-constructivist approaches are used.