The most common problem with gutter systems is that the downspouts get clogged with debris. Using larger 3" x 4" downspouts can help prevent blockage and will drain the water faster before it can run over the top of the rain gutter.
The larger downspout drains approximately 1.5 times faster then the standard 2" x 3" downspout, which drains 7.2 gallons of water per second.
The larger 3" x 4" downspout will drain approximately 1,170 square feet of roof area. The 2" x 3" downspout will only drain about 770 square feet. A 33% difference could be the difference between costly repairs in the future. The larger downspouts are almost self-cleaning because they do not easily clog up or freeze.