I think it is similiar to a job interview - you have two applicants who look the same on paper; same credentials, etc. - but when you meet with them one impresses you as being more of what you had in mind.
I don't know that it ultimately can be objective. By its very nature, formal recruitment forces you to make some value judgements about pnms that may or may not be 100% accurate. Most of the time, it seems to me, it works out.
Then again, who gets married thinking anything other than this is the one??? And sometimes, he/she is - and sometimes, you made an error in judgement!