Whatever you do, I would suggest a little advance reading on Japanese history and Buddhism before going to either city. It will make your visit more meaningful and lessen "temple fatigue."
One of the best sources is a now otherwise outdated guidebook (don't believe either the restaurant and hotel listings or the prices!) called Gateway to Japan. Its sections on traditional Japanese culture and history are excellent, however, down to the point of explaining the different representations of the Buddha and who all those other figures in temple art are.
Once you've read up on both cities, you'll be better able to make a decision.
If you're going in August, be aware that it's miserably hot in Kyoto at that time of year, since the city is surrounded by hills on three sides and there's no breeze to drive away the intense humidity. Dress in loose, breathable clothing, take plenty of breaks, and at the first hint of headache or nausea, go to an air-conditioned place, sip cold non-alcoholic beverages, and wipe your face with cold water if you can.