Just read through the thread, was dissapointed but not surprised to see a bunch of garbage about sword comparisons. Swords are sidearms for both, not primary weapons.
Nah m9, Knights used swords. Yuropeans fucking loved swords up until they discovered pikes, then discovered swords again. Depends on what you're defining as Knights I guess, whole diverse range of people who could claim to be Knights.
Europeans never stopped using spears, all through ancient history. Even with vikings and Late Medieval soldiers, who more commonly carried swords, it was strictly a side arm for use after the battle lines descend into a melee and you don't have room to use your spear anymore (or if it breaks/you get disarmed).
Swords suck against any sort of metal armor, unless you are specifically and intensively trained in how to use armor-fighting techniques with one, and even then it would be more useful to have a short spear in most cases.
Reach tends to be the prime factor in weapon effectiveness; It doesn't matter how sharp and shiny your sword edge is if the enemy can stab you through the throat before you even get within ten paces of striking with it.
Knights used swords after they had finished their charge and broken/lost their lance, since a sword is less effective but easy to wear and able to be used more times, but the common weapon of both peasant man on the ground and knightly nobleman on the horse was a long piece of wood with a pointy end.
Swords became more popular and commonly widespread during the Renaissance, due to the growing popularity of dueling; You can't very easily lug a spear around while going about your everyday life just in case you get challenged to fight somebody, but a two pound sword on your belt doesn't interfere with your ability to do business.
TL;DR: Swords are sidearms on the battlefield or for civilian self defense/dueling.