<p>I would probably have to say, Dorwinnian, Gondor, or Jigh Elves.
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Dorwinnian because no one plays on it, so the people there are mad, and just think about it. Imagine this little kids going, "Hmmm... I wanna have a base, but where?" He starts looking around, and stumbles on Dorwinnian, "Oooh, they're so colourful! I want to build my base here!" I've never actually seen someone join for the colours, but it could happen.
Gondor because it's the most well known good faction, which makes noobs flock to it. You know the rest.
High Elves because anyone's who has ever been on this wikia knows that elven stuff is strong, and I'm pretty sure Rivendell/High Elves have the strongest bow. And then also elves are supposed to be, 'noble' and such, which makes player think very HIGHly of themselves. Get it? HIGHly, HIGH elves, He He. ):