Both Digital Holography (DH) and Phase Retrieval (PR) are techniques for estimating the complex amplitude of an optical wavefield. This information is useful and can be used for example to measure the deformation of rough surfaces or to examine the distribution of particles over a 3D volume. Free-space PR techniques use a propagation algorithm and at least two known intensity distributions (located in different optical planes) in an iterative procedure to estimate the phase. Since the PR problem is under-determined, there is generally not a unique solution and so the DH approach is considered more accurate. In this contribution we first examine how the choice of propagation algorithm affects the PR performance theoretically using numerical simulations. Then experiments are performed where the results from our PR algorithms are directly compared to the phase distribution estimated using DH. Our findings are discussed in a short conclusion section.