[ClayShentrup]

Here's a compilation of the best expert research, arguing for and against PR. https://www.rangevoting.org/PropRep

A. The research compares proportional (PR) methods to plurality voting, the worst single-winner voting method there is. But superior methods like score voting and approval voting roughly double the accuracy (i.e. group welfare) compared to plurality voting. So no, there's no research showing the superiority of PR to these methods.

B. Even in that limited comparison, of PR to plurality voting, the data still is actually not that clear. For instance, Canada uses plurality voting rather than PR, and is rated as one of the most high functioning democracies by The Economist. Meanwhile lots of proportional democracies are far worse than plurality countries. Compare proportional Brazil (and several other Latin countries) to non-proportional UK, Canada, and USA.