For monitoring Netapps, I think LogicMonitor is better, in that it defaults to "monitor everything, all the time". i.e. point it at a NetApp, and all volumes are monitored for latency, usage, etc. All phsyical drives on all shelves are monitored for activity. All shelves are monitored. Add a volume - it's monitored. You dont have to enable latency monitoring for a volume, so you dont get issues where a new volume was added, didn't have latency monitoring enabled in Ops Manager, so you don't know if the DB performance issue was due to volume performance or something else. LogicMonitor will notice a new volume was added, or PAM card installed, and start monitoring it. (And uses the API, so it can get things like per volume ops and latency, fiber channel adapter utilization, etc, and other stuff not available via snmp)
It's also nice in that it can monitor everything else (windows, linux, databases, routers, etc).
Ops Manager is better as far as configuration and management of lots of NetApps, certainly, if you need to set up complex replications, etc.
