I have been looking pretty hard myself just the last couple of days. I've not yet found another dock with the port selection of the OWC dock.
Compare the specs.
OWC dock vs the RocketStor, try:
5 USB 3.0 ports instead of 2,
An HDMI port (with 4k support) vs none,
a FW800 port vs none,
it's $60-$100 cheaper,
and a company that I have had really good customer service experiences with...
I can't think of a reason I'd spend more money to get less on a brand I know nothing about.
Since I have an eSATA external RAID, would like to have seen an eSATA port, but since there are TB to eSATA adapters available, that's likely something I can live with. Been looking for a dock that has both FW800 and eSATA so I don't have to plug one of them into the end of a TB chain , but doesn't look like anyone has them both.
Plus it will permit booting from external drives via TB, FW, ethernet and with 2013 or newer Mac from the USB ports.
The one item the RocketStor does have is separate lanes for each of it's 2 USB ports. If 2 USB ports are enough and you have 2 devices that can actually read/write (make use of the bandwidth) at those speeds, be using them both simultaneously and you're not using TB for those devices, it could make sense for some buyers. They also list conflicting info related to the USB ports - the front page advertises high ouput 1.5A, but their faq says each port is only 1A.