Choice of Maven Repository Manager and NMaven

When using NMaven for .NET builds is there any NMaven specific reason to use one repository manager over another?

Flame bait:
I have used Artifactory and Proximity in the past.  From looking at http://docs.codehaus.org/display/MAVENUSER/Maven+Repository+Manager+Feature+Matrix it seems Archiva, Artifactory, and Nexus are very close in functionality and all actively maintained.

Is there some killer feature I'm overlooking that makes one implementation far superior to the others?