I am a fan of the 10" size, as is my 5'2" daughter. My other daughter enjoys a 9 inch blade, if I recall correctly. My son, who cooks for a living, uses an 8 inch blade. He likes both hte santoku and French chef's style blades.
The ten inch blade gives me a longer slicing stroke, and allows me to chop/mince as much garlic, onion, or whatever it is that I need to process.
The key to the enjoyment of any knife, large small, or anywhere in between, is to maintain that knife, and keep it sharp. Also, use a quality cutting board so as to protect the knife edge. Get yourself a high quality sharpening steel as well, and hone the edge every day you use the knife, both before, and after you are done with the cutting chore.
Remember, happiness is a sharp knife.
Seeeeeya; Goodweed of the North