They are essentially the same product. We OEM it and call is SMSP.
The difference comes with what is done on the back-end. Rather than do streamed backup of the SQL databases and any SMB shares (holding the BLOBs) we do snaps. The build of SMSP also integrates with SnapMirror and SnapVault.
It would be unfair to compare the two products because SMSP only works on NetApp. You're better off asking what NetApp specific features do I get "OVER AND ABOVE" what the base Avepoint product gives me.
Don't sit with a NetApp array in the data centre hosting your SQL and CIFS BLOB and have a side-by side comparison with the two because even Avepoint will lead you towards SMSP.