[Evans, Marv]

I'm by far no expert, but I've installed a few gutter & drainage systems. My take is you most likely want coverage every place water is shed from a slope or tends to collect. I forget where you live, but if it's a area with lots of rain, you should also take into account management of drainage from your roof areas and the areas around your house. I have a roof with a quarter inch per foot slope and a parapet wall all around, so I have drainage basins situated around the edges of the roof with crickets directing water into them. Those drain down into a system of 3 inch plastic pipes (my wife calls it an underground freeway of pipes) to take the water out to the street. I also have a similar drainage system around the periphery of the yard that does the same. I tried to take the whole picture into consideration to manage as much water shed around the house as I could.