I found these two links but both of them does not have a perfect side-by-side comparison. There are some information missing... SolarWinds PM might want to have that corrected 
http://www.networkmanagementsoftware.com/network-management-software-autumn-smackdown
For me, Opmanager interface has been less intuitive, maps were buggy, and getting in touch with support was always a problem... SolarWinds NPM has a better product although some features like the "CCTV view" from OpManager does not have an out of the box equivalent in NPM.