Cointerra has delivered nothing.
I would agree to this statement, but with the following caveats:
Avalon delivered Batch1. People made money. Batch 3 was a ~40BTC loss. So past performance isn't a guarantee of future profits...
20nm is pretty small. Remember Intel is at 22nm and has had problems at 14nm. What trouble could KnC find at 20nm?
If I follow the "has delivered in the past" logic heck I would choose BlackArrow over Cointerra at least they had an FPGA that worked!
As others have said, split your risks. Order one of each