Its hard to say without researching the origin. Could be just a name or could be made by Kessil and just sold by other with contract for name stamps. Kinda like Kroger brand, Kroger does not make it. They just buy a lot in return they put Kroger on the label.
Same thing as a Kessil A150w. Dicon is Kessil. Kessil is just the name for their grow light division. They also do high end photography lights under the name fiilex. Along with multiple other products under various brand names. They are a huge company grow and aquarium lights are a small part of what they do. I have dealt with Kessil and their customer service is great. The Generic Dicon a150 is probably something sold overseas at a cheaper price with no support. When you pay the premium for the Kessil you are also paying for awesome tech support, customer service and a warranty. I would not hesitate buying that light.