My experience with the two services was a little difference.  I have had 4 boards fail between 6 S9s.  The first 3 were from 2 of my earlier machines and were out of warranty, so I send them to Bitmain Warranty in Colorado.  Never heard much back for a couple weeks and when I eventually heard back from then (about 4 weeks total), they apologized send the boards back fixed for free.

My last experience was with the new repair place in LA.  Since the machine was under warranty, I had to send the whole machine.  This also took a month and it wasn't until I opened a separate support ticket that magically my machine was shipped back.

Both took 4 weeks, and cost nothing.   I guess I can't really complain. . On the other hand I did lose 2 months of hashing so it did cost lost revenue.