Sure, lets have two: but look at the links above. I am pretty much convinced userIso just returns  userIsolation(pat::TrackIso). Even in the HTauTau twiki they use chargedIso in their description: https://twiki.cern.ch/twiki/bin/viewauth/CMS/HiggsToTauTauWorkingSummer2013#Electron_Muon_Isolation. 

Anyway, I did cross check this for WBB and I found essentially no difference between the two.