I came across this today and thought it would be of interest to users here - RME explains why their own USB systems work so much better.
Sound On Sound explains this month, why USB by RME is superior to other USB implementations.
Bottom line: other manufacturers use a standard unoptimized XMOS USB chip. This solution is easy to implement, much cheaper, does not require specialized engineering and works with standard drivers. Voila, here comes a $200 interface.
RME on the other hand is going the other possible way, by recreating the USB protocol in an own chip, which fully exploits the limits of the standard (RME Pro Audio XCore). Channel count, latency, clocking, sync, fixes stability issues and more.
Additionally the code can be updated at any time, as the chip is fully re-programmable (FPGA). So even 15 years old RME interfaces still get updates, to work with the latest USB hardware - fast, reliable, usable!
On top of it: To achieve record low latencies with USB, it needs a special highly optimized driver. Only RME is doing both. RME interfaces are using a fully customized USB implementation, to the utter limits of the standard with a special driver technology, which delivers the same stability and speed on Mac OS and Windows. Ever tried to close your Macbook, while playing music and open it later? The music just continues to play, without a single buffer lost.
The article explains also, why USB2 and USB3 are not different, regarding stability or audio latency (except the channel count) and why Thunderbolt is not necessarily better, faster or more stable.
Conclusion: RME USB interfaces might be more expensive, but are faster, more stable, need less time for bug fixing, get all the driver updates and features in time and thus can be used 10 years or more with a high resale value … and of course sound great.