Correct me if I'm wrong (please!) but FreeNAS still can't (easily?) do what Synology's 'Hybrid RAID' (basically sharded RAID across drives) facilitates; growing your (redundant, e.g. 1 or more parity drives) volume by adding more drives, and also growing your volume by replacing drives with larger ones.

I've always thought that was essential, it bemuses me that there aren't many solutions out there that help you do this. I guess everyone must buy have loads of disposable income to buy 8 drives at once.