What is the difference between Delta frequency converter and Fuling frequency converter?

Delta frequency converter is well known. Only series b is available. It seems that E series is much worse than Fuling frequency converter. I bought Delta frequency converter before, and the after-sales service was too poor. It will take more than half a month to repair a machine during the warranty period. Without a spare machine, they will not come to the door. Fuling is much better. Last time my machine broke down in the factory, I was on-site service.