Bicoptor's approach differs from existing methods in improving the efficiency of evaluating non-linear functions by introducing a novel sign determination protocol that allows for faster computation without preprocessing. The key difference lies in the use of repeated truncations to determine the sign of an input, which enables a more streamlined and efficient process compared to traditional methods. By optimizing the communication rounds and eliminating the need for preprocessing, Bicoptor significantly enhances the performance of evaluating non-linear functions in privacy-preserving machine learning.