In previous works, the authors showed that using robot-assisted steerable electrode array insertions can significantly reduce the insertion forces compared to non-steerable electrode arrays. In addition to steering the electrode array, it is possible to change its angle of approach with respect to the scala tympani. This paper focuses on determining the relevance of changing the angle of approach of the electrode array by comparing steerable electrode array insertions using a two Degrees-of-Freedom (DoF) robot versus a four DoF robot. Optimal insertion path planning strategies are presented for both two and four DoF insertions. Simulation results and experiments show that the four DoF insertions can improve over two DoF insertions. Moreover, changing the angle of approach can further reduce the insertion forces. The simulation results also provide the workspace requirements for designing a custom parallel robot for robot-assisted cochlear implant surgery.