This document compares the performance of two types of low-profile sinuous antennas - the Duhamel and Vahdani sinuous antennas - for ultra wideband applications. It finds that the Duhamel antenna has a wider bandwidth but more uniform gain, while the Vahdani antenna has approximately higher gain and is more directive, making it suitable for applications requiring high gain. Both antennas exhibit good radiation patterns and input matching across their operational bandwidths. The Vahdani antenna also has the advantage of a lower input impedance, improving its feeding system design.