Quantitative comparison with methods which have different number of vertices!

Thanks for your great work! When evaluating 3D face reconstruction , The ECCV paper compared with 3DDFA which is based on BFM. The difference between 3DDFA(50k) and PRNet (40k)is the number of vertex, when I use 3DDFA, how can I compare with PRN in AFLW2000? Look forward to your reply!