I tend to agree with others in that in the end it probabaly really doesn't matter but I will throw in my two cents anyway.

I think leaving buttons unbuttoned is a sign of being in the know and entirely comfortable in your clothes. It is maybe even a touch of the elegance that comes along with the non-chalant details. I liken the the bottom couple of buttons on the waistcoat to leaving a button unbuttoned on the functioning button cuff or leaving the bottom button of a 2 on 6 double breasted jacket unbuttoned or not buttoning all buttons on a 2 or 3 button jacket or not wearing matching tie/pocket silk sets. I think it gives a sign that you are comfortable in these types of clothes and don't feel like you are in a straight jacket.

How many guys have you seen at a wedding or funeral that dragged their suit out for the first time in five years, buttoned both buttons on the two button jacket and looked like their suit was some sort of torture device?

In closing, wearing clothes with a touch of personality and style is more than just putting them on.