Many times we think if we install a larger new gutter and spouts on a low slope metal roof or shingle roof with a problem shedding the water it will stop the leak . Almost Never or very rare! This is normally a difficult leak to stop. Generally the roof has little or no slope or has gutters and spouts that not been maintained on a schedule.
Actually gutter can be your homes “enemy” if it is not properly maintained. Gutter is a great tool to divert water on an upper story home or a home with drainage issues. But if you have gutter or are purchasing new gutters and spouts they require frequent maintenance when trees are overhead or nearby. The increased capacity of the new gutter will rarely excuse a leak. I believe gutters are necessary to control or collect rainwater around your home but if trees are close to the home make an agreement with your Lawn maintenance professional to keep gutters and spouts free of debris.