TKO is the biggest.
PAN is the next biggest and usually wins ANW (but not last set)
ESD is the really good small netgaining clan (and won ANW last set)
LaE is new-ish (existed in the first sets, but is only in their 2nd set back) and is about PAN's size and has a lot of good veteran players as well.
Honestly, I'd campaign more for PAN, but TKO and PAN are having suicider issues this set, so while this is bad recruiting on my part, if you want to be sure you're safe to netgain, (this is odd to say) LaE or ESD are probably your best bets.
However, we in PAN would still be happy to have you, and I'd imagine since you'd be one of the smaller guys in the clan, you'd probably be safe, since the suiciders mostly have tended to hit bigger guys or Juusto (who is probably our most active killer).
If you're interested, hit us up:
http://www.eepandora.com
One thing I can say for a fact, suiciders or no, is our site is better than LaE's :P