There is no selection criteria in selecting a bounty campaign manager because all are good as campaign managers. Among all the campaign mangers, I think yahoo has got the highest trust level and he is prompt and perfect in managing campaigns like counting the posts, issuing the payments without delays etc. But I don't think he will accept to manage a bounty campaign. I think Irfan is accepting bounty campaigns. Just contact him and see.
I did see for sometime that yahoo do have a bounty campaign recently I don't know whats the update on that,this is why its quiet odd that Yahoo did enter on bounty campaigns too considering that hes only handling Bitcoin signature campaigns.Since we are talking about bounty managers then according to my own ranking (without reference) Ill choose Sylon or Irfan_pak. I did see these two managers shows professionalism on handling bounty programs.