Recent advancements in electromagnetic machine design have driven significant interest in coreless topologies employing planar coils, owing to their lightweight structure and manufacturing advantages. This study presents a comparative analysis of four planar coil variants integrated into a Dual-Rotor Single-Stator Generator (SSDR), aiming to evaluate and enhance electromagnetic performance. The investigated coil geometries include Planar Square Coil (PSC), Planar Rhomboidal Coil (PRHC), Planar Trapezoidal Coil (PTC), and Planar Rectangular Coil (PRC). Finite element analysis (FEA) was employed to assess critical performance metrics such as coil flux density, magnetic field distribution, and flux linkage for each configuration. The results indicate that the PTC demonstrates superior electromagnetic characteristics, exhibiting an optimal flux distribution profile and high flux linkage. Among all tested variants, the PTC outperformed the PSC, PRHC, and PRC by 2.5%, 2.2%, and 1.75%, respectively, in overall electromagnetic performance. The PRC followed closely behind in terms of flux linkage but showed relatively less uniform field distribution. This comparative study underscores the potential of the trapezoidal planar coil for use in lightweight, high-efficiency SSDR generators. The findings provide valuable insights for optimizing planar winding designs in next-generation coreless generator applications. Future work will focus on experimental validation and thermal performance analysis of the proposed configurations.