Which is the best?

[s0lembum]

I m going to start playing this again but which server is the best, crowded server or the others ?

[Flexxzorz]

Lordaeron is a 'hardcore' x1 server, never had any issues with the population. Always lots of people online and no lagg.

[Firnblut]

Lordaeron is the most crowded server. It is also the server which will give you a most retail-like experienec. Keep in mind though that it's a custom server after all.
Raid difficutly has been adjusted to be a greater challenge, heirlooms have been removed, RDF is not available and most probably wont ever be.
I bet there's more i forgot to mention but pve-wise it should cover the most important changes.

[taralej]

The question you should ask yourself is whether you are willing to play on a 1x realm with limited content, which gets released gradually, and disabled RDF, so you have to group and travel to dungeons. If you like these things, then Lordaeron is for you. If you find them encumbering, then Ragnaros or Deathwing are the better choice.