The lightest pressure possible will give the sharpest edge. It's ok to use a little (very little) pressure at first, especially on the coarser hones. Once you get to 4k and above, the results of using less pressure becomes quite noticeable. I always end my strokes on each grit with as super-light a pressure as possible, especially the last 5 to 20 laps(depending on the hone).

Less blade flex? Smaller striations/teeth on the edge? Less "micro-burring"? The technical reasons why are beyond me... it just always seems to work out that way.