Girtablulu
Just go for Synology. Their Software is miles ahead of the competition (for consumers) in terms of ease of use and performance.
I just switched from QNAP to Synology last month and don't regret it. The hardware in the QNAP was actually better but the software ran like ass. E.g. long boot and shutdown times (we are talking 5 minutes ++) which is apparently normal for QNAP. The Synology NAS just boots / shuts down at normal speeds and everything is snappier.
They also seem to have a good track record for delivering updates to their OS for a long time. A major update is planned to be released this summer and apparently even NAS models from 2013 are going to get updated.
Just make sure to get a "+" model, e.g. the "DS220+" or the "DS720+" with an x86 CPU. Those support BTRFS as a file system with data scrubbing / auto healing features for mirror / parity raids. And don't worry about the problems BTRFS still seems to have with RAID. Synology doesn't use BTRFS to create the RAID so they are not affected.
And as far as backup functionality goes, the software Synology has for that is actually good. You can backup the NAS itself, Windows clients (iirc Linux support for client backups is in coming soon too) and combine that with BTRFS snapshots.
So far I have used QNAP, Thecus and Synology as far as NASes go.
Right now I'd rate them: Synology > Thecus > QNAP
