The Golay Code Outperforms the Extended Golay Code Under Hard-Decision   Decoding
  We show that the binary Golay code is slightly more power efficient than the extended binary Golay code under maximum-likelihood (ML), hard-decision decoding. In fact, if a codeword from the extended code is transmitted, one cannot achieve a higher probability of correct decoding than by simply ignoring the 24th symbol and using an ML decoder for the non-extended code on the first 23 symbols. This is so, despite the fact that using that last symbol would allow one to sometimes correct error patterns with weight four. To our knowledge the worse performance of the extended Golay code has not been previously noted, but it is noteworthy considering that it is the extended version of the code that has been preferred in many deployments. 
Jon Hamkins
cs.IT math.IT