Given multiple designs with the same elements, how does the balance of elements help a design to make it more favorable / effective than the others?
A feeling of order and tidiness, that leads on a feeling of rightfull/good, and good readability.
As human being we tend to give meaning to things, as well we tend to organise the caos that surround us, just because it looks in disorder, like could be a desk or an house. Having information organised on a invisible grid helps us to achieve this order of things. Organised information help us as well while we are scanning a page, to know where to expect an information once we have learned the pattern of how things are organised (like the number of a page, or the location of a navigational web menu full of links).
In this organization it is easier as well to attract attention on a single details just moving this single details out of the pattern to be more evident respect to the others elements.