Re Sioux City and DHL ... we certainly can find examples on the fringes where the heavy crew has a better chance of survival.
Equally, we can find examples where an ill-disciplined three man crew performed rather indifferently.
The real world reality is that the Industry is headed toward the well known "one man and a dog" crewing philosophy. It's not going to go in reverse so we all had best get used to it and adapt to the management demands in the cockpit.
The flight management reality is that the commander has to apply an increased level of interest to optimal crew management to overcome any shortcomings in the smaller complement.
Me ? I was quite happy either with 2- or 3-crew where the company philosophy was to overtrain and the crew members were both experienced and competent.
Nowdays, with a management hat on .. I just hope that the folks up front approximate well trained and highly experienced/competent.