[Derision]

Supported clients are:

Titanium
Secrets Of Faydwer (off the retail disc, NOT any digital download version).
Seeds Of Destruction (only the digital download version currently available on Steam).

Titanium has been supported for several years and is the best supported currently.

Seeds of Destruction is the newest supported client and is getting the most attention at the moment and is generally considered superior to SoF in terms of stability.

You should be aware that not all the public EQEmu servers support clients other than Titanium, for their own reasons. TZ/VZ comes to mind, so if you go for SoF or SoD, you won't be able to play on those servers.

Likewise, since the public login server doesn't yet support SoD, you will only be able to play on a few servers with that client currently.