I only have the 56 and I like it a lot. The 90 does have the edge, also in sharpness. But the focal length is difficult for me. The 56 is already hard to use indoors, you get very tight shots. Just imagine the XF 90 here.
I think those kind of parameters are more important in deciding between the two than the quality of the blur or lens sharpness. The latter two are so close that you must think well of you use cases.
