This post from John Smart on the Wakaleo Consulting blog summarizes the results of a preliminary comparison of Nexus and Artifactory. In this post, Smart compares Nexus to Artifactory in the following areas: Installation and General Use, Artifact Searching, Security, Build Promotion Strategies, Deploying Maven Web Sites, and Repository Maintenance.
Here is Smart's conclusion:
This comparison is far from complete. Both Artifactory and Nexus are solid, feature-rich products, and the competition is good, as it keeps both product teams on their toes. My personal recommendation however goes to Nexus, as in my opinion it has better support for the requirements of larger organisations, and is nicer to work with in the context of build pipeline automation.
To read more comparison and analysis, read Smart's post on the Wakaleo Consulting blog.