I would just check this forum and see what others say about the brands you are considering.
If you value warranty/honesty and/or your time you can cross OG-Evkin off your list. So only 2 more to go 
After checking prices, listening to your advice about the brands, and discarding OG-EVKIN due to the warranty and contact problems that some of you have had.
So I have the Velobuild and the TanTan, which only vary in price by about 10 dollars between them.
According to you, which of these two distributors is the best in after-sales service, which one would be more reliable?
Thank you very much again for your answers