Exactly, it's a little bit difficult to find related examples except matthew mentioned. The link is out of date and the update one is here:
It contains lots of figures, perhaps they are what you want.
First of all the name of backends (devices) has nothing to do with their location! They are all located in US.
Back to your question, as others already mentioned the difference is in the architecture (topology) and the error rates.
If you click the name of any backend (device) in your IBM_Q Experience dashboard, you'll see detailed information about the ...