I've conducted tests on similar questions for my day job, and having the arrow consistently in a predictable position proved to be far superior.

Sorry, I can't provide hard data as it's company confidential, but consistency of position has become one of the main design driving forces, so clear was the evidence.

I would be interested in knowing why you claim to be indifferent to it. My tests showed people thought it didn't matter, but their actions were significantly more efficient. Some didn't believe the results, even when shown the measurements.

Why do you think you are indifferent?