An inch increase in diameter give you much more load than an inch increase in pitch. Mass only has an effect when going from idle to full throttle and back. Your engine will take longer both ways with a heavier prop. Also, due to the inertia of a heavy prop, your airframe will be subjected to more intense vibrations.

If your plane is to fast, go one inch up in dia. and one inch down in pitch. So I'd say a 14-5 or a 14-6. Take her out for a spin and see how she does.
Finding the right prop for a plane-engine combination can take a few tries, but it is well worth the time.