Unitrends vs Cloudberry/S3 - which would you choose?

We are investigating a possible switch from AppAssure to another backup solution. We are currently backing up 18 servers (all but four of which are VMs). Around 5TB of (de-duped) data. One Exchange server. Four SQL servers. When it's working, AppAssure has handled all this fine, including offsite replication.

After searching these forums I'm taking a hard look at Unitrends. Another suggestion was Amazon S3 + Cloudberry. We are a non-profit performing arts org, thus highly price sensitive.

I don't find much comparing these two. Can anyone offer any insights? 

Thanks.