Which is the best EU Server to choose?

[Monsalvato]

But where is your answer based on?

Personal (and statistically not relevant I suppose) experience with the servers and research on some guilds/communities which will call those 2 servers their home, respectively.
A lot of people on Odin for instance (and even on Cerberus, to a lesser extent) really loved FFXI's "international" feel on servers, and are trying to do something similar. Of course it will never be the same (thanks Yoshi-P -___-'' ), but a lot of people share the sentiment so I have a good vibe about it.