Odin is very populated, as it is one of the first server that went 'full'. Also I think it's currently the #1 English Speaking Server, some tend to have more french or german people. Odin is more or less, English!
At midnight it does get abit more empty, but not completely as people log in from different time zones - so there's still enough to do 24/7.

That's my take on it! =)