Scale related to the space you are working with is a prime consideration."Consider the size of the area, says R. Patrick Worzer — Land Design Services, Inc. "You may wish to use large stones in a "field" area, but then use smaller stones as border."
Ed Dermody of Woolpert says this question is often be a critical design decision. "It should be based on the several design principles. Larger pavers are masculine in nature that will create a heavy footprint while decreasing the sense of size of the patio. Often times this is a result of larger pavers being more unique in the marketplace and because of this, they become more apparent and demand visual attention. The smaller paver is simple and more common with greater design flexibility. Smaller pavers will also create a sense that your patio is larger and more spacious."
Doug DeLong agrees the size of the space determines the scale of the pavers. "In general, the size of pavers should relate to the size of the space. However, there are a lot of examples of successful small spaces using larger pavers and vice versa."