The higher up in the list, the less the population is. The most populated servers are at the bottom, like the newbie Stromm server. The Legends server is always at the top since almost no one plays there. I played on Povar for a time, and it seemed like a nice, medium populated server.
I now play on Kane Bayle, which is always just a little bit more populated than Antonius Bayle on the server list. I'm in Pacific Time, I know lots of people who are PST also, and even when I'm not playing with them I can more often than not find a quick LDoN pickup group each night. Earlier is definitely better--if you don't get into a group by 9, you probably have to wait until that round of LDoNs ends and you can get in on a group who is losing a member or two. At 10 PST you'll probably see around 75 in PoK, then it will go up to near 100 before midnight, then drop back down to 50 after. I have never seen more than 150 people in PoK though.
Game on,