Sonalksis CQ-1 is my favourite so far.
Haven't yet tried the Sonnox one.
I prefer these over a standard singleband plugin.
The nice thing about a multi is being able to pull out the ess whilst dynamically opening the topend so it doesn't get too dark.
Only downside is they are very level dependant, a good deesser should be able to remove (or at least detect) the ess at any level with an unwavering amount of G.R - essentially always maintaining the balance between broadband and de-essed signal.
Good de-esser 
Bad de-esser 
Rane article for more:
Dynamics Processors - Chapter 4
A quiet ess might not trigger the CQ-1 etc but could still sound bad. So automating the threshold helps, could also play with feeding the de-esser from a ext. key input which is the vocal track heavy limited (and filtered) to ensure all ess's make it over the threshold.
Just my 2p.
-T