The study of sparse linear arrays has started in the 1960’s and remains a hot topic. Since then, the problem has been approached in a variety of ways, and many different optimization algorithms have been used to design sparse arrays. In the early years of sparse array research, in addition to other methods that involve array pattern related measures, the problem had been handled in terms of the coarray structure. Such methods do not directly involve pattern-based objectives, and in some cases, they have closed-form structures; we call these methods as coarray based methods. Nowadays, coar-ray based methods are attracting considerable attention again. In this paper, the analysis and comparison of the most commonly known ones of those arrays are conducted. Moreover, the necessity and the success of those arrays are discussed by chasing answers to two questions with simulation results. First, while keeping the number of sensors fixed what is the optimum layout? Secondly , while keeping the aperture fixed what is the optimum number of sensors to be used?