For balancing reasons, weapon of choice only allows selecting a single weapon within a weapon group instead of the whole group. The feat can be taken multiple times as a bonus during epic levels, though.
Ki critical now grants +1 to the threat range of their weapon of choice instead of the usual +2.
Example: A weapon with increased multiplier would go from 19-20/x3 to 18-20/x3 and not 17-20/x3.