Straight damage calculations can be misleading. Firstly, there are many opponents not subject to criticals. Secondly, it increases your attack bonus for opposed checks (such as Disarm or Sunder). Thirdly, extra attack bonus not only increases the likelihood of hitting (and damage), but can be traded off in some circumstances, e.g. Combat Expertise or Power Attack.
Also, MWM is more flexible, in that it can apply to a range of weapons. And given the proliferation of the 'golf bag of weapons' syndrome in 3.5E, this needs to be considered.
Also, MWM is more flexible, in that it can apply to a range of weapons. And given the proliferation of the 'golf bag of weapons' syndrome in 3.5E, this needs to be considered.