The open mesh guard is probably the least effective due to the size of the holes in the guard. Steel accumulates thousands of pine needles resulting in you having to pick them out one by one to clean the gutter guards. The perforated gutter guard will keep out 90 percent of the pine needles. Eventually, some of the small one eighth inch or smaller diameter holes drilled in the periphery will collect some pine needles. The few pine needles that get stuck will stand up straight in the holes.
Sometimes this can cause other pine needles to come down and hold against the ones that are sitting vertically in the gutter guard holes.