I've got a Pegasus 2 R4 and a StarTech dual bay thunderbolt enclosure with a couple of 1TB Samsung Evo 840 SSD's.
The Pegasus is quite a professional unit, well for desktop storage it is anyway and it's very quiet.
I got the StarTech to run VM's from SSD, but the Pegasus has been that good that I don't use the SSD's. I've also found the throughput of the StarTech to be fairly slow - around 350MB/s, much slower than the SSD's can deliver. The Pegasus is delivering around 600MB/s using the HDD's that came with it.
I've also got a Drobo Mini, but it's sat in a drawer. It's noisy, slow and gets very hot. It might be useful every now and again when I'm on the road, but otherwise I won't use it.
I backup the Pegasus to a Synology 412+ NAS, using a mixture of TimeMachine and rsync, depending upon what I'm backing up.
If I were to buy again now I'd get a Pegasus R4, maybe an R6 and the new Pegasus M4 with some SSD's. Their products aren't cheap but you do get what you pay for. I'd still keep a NAS as a backup.