The 2.5GHz Asian HTC One (M8) has gone up head to head against the 2.3GHz US HTC One (M8) version in AnTuTu, where initial results to seem to put both devices to be on par in terms of performance. Perhaps the rather similar performance capabilities in both devices could be due to a non-final testing unit being used in Asia, or a different kind of RAM as well as storage. It is rather difficult to draw a distinct conclusion between the two, despite the Asian model sporting a 200MHz advantage on paper.
Only time will be able to tell as folks start to tear down both devices to check out the innards and the quality of the parts that are in use. I am quite sure, however, that regardless of whether you settle for the US or Asia version, either one would be as tough as nails.