Argumentation is a reasoning model based on the construction and the evaluation of arguments. In his seminal paper, Dung has proposed the most abstract argumentation framework. In that framework, arguments are assumed to have the same strength. This assumption is unfortunately strong and often unsatisfied. Consequently, three extensions of the framework have been proposed in the literature. The first one assumes that an argumentation framework should be equipped with a (partial or total) preorder representing a preference relation between arguments, and capturing a difference of strengths of the arguments. The source of this preference relation is not specified, thus it can be instantiated in different manners. The second extension claims that the strength of an argument depends on the value(s) promoted by this argument. The third extension states that the set of arguments is equipped with several preorders; each of them expresses preferences between arguments in a given context. The contribution of this paper is two-fold: first, it proposes a comparative study of these extensions of Dung's framework. It clearly shows under which conditions two proposals are equivalent. The second contribution of the paper consists in integrating the three extensions into a common more expressive framework.