I too had wondered about homefield advantage for Benoit.
However, I also think that Sweet Chin Music is the perfect kind of move for an Ironman match. Quick, sudden and deadly. An instant fall should HBK land it. Benoit lacks anything even remotely similar.
To my mind, Michaels also has the more pronounced mean streak that would allow him to use underhand tactics such as lowblows and eye gouges or to accept a DQ for the chance to blast Benoit over the head with a chair.