The Brodak kit is more true to George's original airplane as he flew it in the early 50's. Top Flite bought the rights to it and they and George refined the design and made some changes in order to get the kit into a standard box and to also ease construction some, such as the molded turtle deck and such instead of carving blocks. The big blocks take up a lot of room in a kit box, for only most of it to be cut away!. The preformed sheeting was lighter and also cost less in the long run because it used less balsa. The biggest difference between the designs is the amount of wing asymmetry, with the inboard wing bit longer on the Brodak kit than the Top Flite kit. Lots of opinions on which is best. There were a couple of other Noblers before this one that Brodak kits, and the Top Flite version is referred to as the "green box Nobler" by many due to the green labeling. There was also a follow up version called the Gieseke Nobler with some changes and mods that Bob Gieseke made to the green box kit and with which he won several NATS with. Build yours as the instructions say and you will have fine flying airplane.
Good luck and have fun,
Dan McEntee