My preferred method of measuring my body fat composition is by underwater weighing.
Underwater Weighing involves methods from the principle which states that when a body is submerged underwater, there will be buoyant counter force equal to weight which is displaced. It uses Archimedes principle of displacement. The higher the percentage of fat, the less displacement of water.
This is more accurate because if the guidelines are being carried out properly, it will have +/- 1.5% error. This method is considered the "gold standard" in percent body fat measurement. Repeat measures also mostly prove consistent, and can be used to chart progress. Hence, it is rather reliable.
However, it requires a lot of equipment and space, testing is time consuming and involved as well.