I do not have any test data to substantiate the following but have always understood this to be the case regarding solid "moly" (Molybdenum disulfide) as found in greases:
****Do NOT use moly greases in wheel bearings or in the steering head bearings. Moly tends to change to stiff flaky bits if used in those roller bearing applications. As a general rule, do not use moly containing greases, oils, etc., at any place there is rotational speed differences, or in ball bearings, needle or roller bearings, and most sleeve bearings. Moly is GREAT for most SLIDING surfaces.
It might be better to think about the application and then make a decision. Why do you need moly in this application? For wear protection? For lubricity?
There are plenty of established greases that meet specs such as NLGI GC-LB that do not contain moly and function very well in wheel bearings. Additional thoughts?