If you are looking at the Probox, e.g. HF7-SU31C, this is USB3.1 with type C and supports 10Gbps, where the standad USB3.0 units with type B support 6Gbps. So there is an improvement on the interface, noticable only when using SSDs. Using standard HDDs, it is same slow. Using HDDs (which is likely due to size), you can save your money and go for USB3.0. Even in 5 years the interface won't be faster.
So I'd say if you want to go for SSD, go for USB3.1 interface (or 3.2 if available), which will typically be type C.
Most importantly, check the specs of the box!