Which countries?
PR has always struck me as the most "fair" system; if 2.8% of the electorate favour the octopus nostril party*, then 2.8% of the seats in your house of parliament will go to the nostril boys. However, I thought that in practice it tends to rarely return a majority government; meaning the largest parties end up having to form coalitions with fringe (often pretty crazy) parties; meaning that the aforementioned eight tentacle lovers end up getting far more leverage in their nation's politics than their vote percentage would support (as they end up being key to holding up a coalition).
* Randomly chosen to avoid using <insert fringe party that will upset someone because they actually support said party>