The long rods swing slower than the short rods. This is because each of the rods has a resonant frequency. The resonant frequency is a measure of how often the rod to swings back and forth in a given amount of time. Resonant frequency in this exhibit depends on a number of things. A heavy rod needs more energy than a light one to get it swinging.
More energy is needed to reverse the swing and make it go the other way.
Another factor is the springiness of the rod. If the rod is really springy, it forces the weight back and forth very quickly. If the rod is not springy, it will ease the weight one way or the other with much less force. An additional factor is the length of the rod. If the weight is at the end of a long rod, it will have to travel a long way to get to the end of the swing and that will take more time.