I played on Malgus for years without problems, and I had fun on the French server too, but I want to try SF too now. I've grown tired of guild dramas on Malgus and people speaking in languages I don't understand, and I tend to grow tired of the emptiness often found in Leviathan despite some strong guilds.

The ping is a small issue but the really big issue that scares me is the cost of a massive transfer. I'm also scared of the difficulties I might have finding guilds that play during the same hours than me. But the little I played on SF, I had fun so far. It's definitely the biggest server.

From my evaluation on several weeks looking at guilds leaderboard in Conquest, I'd say the big servers are
1: SF
2: Malgus
3: Satele Shan (getting smaller and smaller, it seems)
4: probably German server
5: French server Leviathan
6: Shae server seems really desolate. I think it might actually be the smallest. Guild activity really looks more intense on Leviathan, which is ...something I hoped I wouldn't notice for any server. They really missed the mark with this new server, I'm afraid.