Student's t test assumes normal distribution of samples, sign test assumes paired samples where values on the same input row form pairs. For t test the Meta.Numerics presumes equal variance in both samples. Option Codes and values enables simultaneous U and t test for multiple samples and up to 255 variables. For Kruskal-Wallis test the input lines must be in columns: grouping code and values.
U test is sensitive to exactly equal values and different algorithms are used (Bergmann et al 2000).