Digital predistortion (DPD) exploiting the Volterra series can effectively compensate the strong nonlinearities (with memory effects) of power amplifiers. Diverse pruning schemes have been proposed to reduce the computational complexity with comparative performances. Regrettably, the mechanism of basis construction in different DPDs that is related to the complexity-efficiency tradeoff has not been well-studied. In order to compare methodically the Volterra-series based DPDs, the key parameters of the basis are studied here. Especially for the cross terms that describe the interaction between nonlinearities and memory effect, the complexity-efficiency tradeoff cannot be addressed directly. Thus, the basis construction of DPDs is firstly mapped to the general Volterra-series to observe the pruning property of each DPD. The diagonal dispersal property on basis construction is concluded as the most efficient and reliable way for pruning DPD techniques. The running complexity-accuracy tradeoff is quantitatively analyzed via the number of floating point operations. With the best performance settings found by the Qhull algorithm, the experimental results show that (1) the nonlinear order of the cross terms is more significant than the related memory depth, and (2) basis construction with diagonal dispersal properties effectively shows the complexity-efficiency tradeoff of different DPDs. These results offer new angles to assess the feasibility of DPDs and their involved complexity.