The goal of this paper is a thorough investigation of the quality of the software tools widely used nowadays in the field of planar-antenna analysis and synthesis. Six simulation tools - five well-known commercial tools and one developed in-house - are compared with each other for four different planar antennas. It is crucial to point out that all possible efforts have been made to guarantee the most optimal use of each of the software packages, to study in detail any discrepancies between the solvers, and to assess the remaining simulation challenges. The study clearly highlights the importance of understanding EM simulation principles and their inherent limitations for antenna designers. Finally, some designing guidelines are provided that also can simplify the initial selection of EM solvers.