> I assumed those two ways might have slightly different values but the same pattern. While when I
> checked the results from two methods, they did show a very similar contrast pattern, but the statistical
> value range differ a lot. The activation from surface data were more robust ( a lot).

It is hard to assess the similarities between the two results since you didn't show the color scheme. It would even be better to compare the two without any thresholding. Nevertheless, it might not be too surprising that the surface-based approach is more sensitive due to its higher accuracy in terms of spatial alignment across subjects.

Gang