9" or 14" diameter air cleaner?

Diameter has little bearing on performance ... on a street ride. Theres a few good reasons to use a larger diameter air cleaner.

Larger selection of fliter sizes.
More area of filter.
Gets dirty/cloged slower since theres more area.
More area to draw air from

Since performance is the goal, IMO, a K&N extreme lid and filter (Comes with base and instructions) is the way to go.