Kraken (Zircon - Low Rate)
Tons of quests / new items / new maps
Items Crafting / Honor System etc
Leveling is hard / slow after 60
User count around +30 now
Top Level 61
Mirceless (Zircon - Medium Rate)
Tons of quests / new items / new maps
Leveling is easy till 50 & afterwards too
User count around +20 now
Mir3 / Mir 2 Maps
PVP system
Top Level 61
2 new areas, an achievement system and a guild leveling system coming in 2 - 3 days
Olymp (Zircon - Medium Rate)
Tons of quests / new items / new in game stuff
Leveling is easy till 50 & afterwards too
User count around +30 now (50% of them are miners)
Mir3 / Mir 2 Maps
Top Level 75
Every server has different leveling speed, quests & in game systems. Spend some time in all 3. You will enjoy all of them.
Personally I am playing Mirceless. Enjoying a lot.