First Past the Post (FPTP) elections, as practiced in the United States and the United Kingdom are considered by many political scientists to be inherently unfair, due to the way in which districts are created. On the other hand, Proportional elections remove many of the restrictions of voter districting, which also removes the threat of gerrymandering.
for more information:
FPTP https://en.wikipedia.org/wiki/First-past-the-post_voting
Proportional https://en.wikipedia.org/wiki/Proportional_representation