Coming from England I play EU servers mainly, if I am up late sometimes I play on NA servers and generally have a good experience on those barring alot of chat rage sometimes. NA siege though, I don't know what happened to it as it used to be fine, but I played on it again last night and half of the players just spammed side swings at enemies who were on the OTHER SIDE of a team mate.
I lost count of how many times I was slashed in the back when I was simply standing on the spot or moving within a 1 metre square, also see many team mates run into a group of other team mates who were killing an enemy, spamming sideswings and wounding them all and not even touching the enemy.
Overall I'd of course have to go with EU, I seem to come across less side swing spamming team wounding players and more players who actually play for the team, rather than themself. I also feel the level of skill is higher on EU in general, I come across far more hard fights on EU servers than I do on NA, but that is most likely down to the fact there are just more EU players thus there is generally alot more highly skilled players. I also saw more chat rage on the NA Battle server last night than I have seen on the EU servers in a whole week, probably two.