Tough decision I have operated both saws and own a 5020 because I also own a limbing saw. If you decide to just keep the bar and use this as a primary saw I probably would just stick with the 18 and accept the power loss. The 5020 is heavy and over time can be potentially fatiguing to use as a limbing saw and thus prone to lost time sharpening chains when cutting limbs near the ground however if you decide to retrofit the 5020 with a 16 inch bar I would certainly pick this combination for the extra power and reduction in weight. For an idea of reliability my saw starts very easy cold but in its 3rd year already is starting to show some sighs of potential repair as the saw needs to cool off some in order to restart.