BlackMax and Poulan/Weedeater are different brand names for what are essentially the same products manufactured by the same company.
BlackMax products are manufactured by Husqvarna AB, aka AYP (spun-off by Electrolux, and owned before that by Sears/Roper). They manufacture a wide variety of OPE products under a number of different brand names including Poulan/Weedeater, Redmax/Ryobi/Zenoah, Jonsered, McCulloch, Ariens, Flymo, most Craftsman OPE products (up till a few years ago), and many private label store brands (including BlackMax). Many of the products they manufacture are built-cheap-to-sell-cheap to compete in the low-priced OPE segment, but they also manufacture some better quality products. Most of their cheap handheld OPE products are now manufactured in China by Jenn Feng, a manufacturer that Husqvarna purchased a few years ago.