Kievan Rus (as Kievan Russia is often called) differed from Western European feudal states in two key areas. First, western European states largely consisted of more or less indepedent towns and cities that pledged tribute and loyalty, unlike Keivan Rus.
In addition, western European societies were divided into different social and economic classes, with a large segment of serfs at the bottom. Kievan Rus society was not separated to the degree of feudal states to the west in terms of class.
One could also argue that Kievan Rus was more technologically advanced than western Europe, as it was at the heart of important trade routes, which brought both prosperity and new technology.