In this paper, we study the dynamics of legal convergence and the comparison between the different instruments of legal convergence based on cooperative strategies (i.e., harmonization and unification) or not. To study these questions we use a model with two nation-states which is inspired in part by that used in Carbonara and Parisi (2008) where preferences of each nation-state are such that it is costly to change the law, but it is also costly to have a different legal system from the other nation-state. We show that legal unification could be achieved in the long-run through small step by step changes despite the existence of huge harmonization costs in the short run. We also show that legal cooperation is not always necessary to achieve legal convergence.