Investigation is conducted on the computational efficiency of van den Berg's integrated-squared-error algorithm with different variational basis functions (VBFs) when applied to dielectric problems. Members in this family include the Matrix interpretation of the Spectral Iteration Technique (MSIT) and the well-known Conjugate Gradient FFT (CGFFT)-each arises from choosing an appropriate form of the VBF. A third choice which is based on a generalized Neumann series (GNS) expansion of the inverse of the defining integral operator is shown to give much superior performance than either the MSIT or the CGFFT. Tests performed on a variety of object shapes and dielectric materials indicate that the GNS is the most efficient among all three FFT-based methods.