There are reasons to chose the ladder rack, or cieling based system. First of all, it is cheaper, in almost all cases. Second, according to most of what I have read, cooling from above, and not the raised floor type of cooling is more efficient overall. This does make sense, as cold air falls... In addition, in most cases, running cables above the racks is an easier and more organized process than being forced to put them underneath, forcing you to lift up tiles, go around all sorts of supports, etc.

I'm not saying that you are an idiot for chosing raised flooring, if you have compared the two methods and deemed raised floors to be better for you, good. I just see no reason for it in any setup I may have.