Steve C

Interesting question.  My initial reaction is that when I was taught Six Sigma 20+ years ago by MBBs with a Motorola>Allied Signal or GE pedigree, they were very insistent that DPMO and RTY were the only acceptable ways to measure process performance with attribute data.  I did not completely agree, and still don't. 
 
I would use yield data for simple products of moderate to low value, since you don't want the burden of your defect tracking system to be a large percentage of the product cost.  You do capture data that can be turned into DPMO in your lower level cause categorization for defectives, i.e. a Pareto analysis.
 
I would use DPMO or DPU for more complex products, since yield would tend to summarize performance to a level that would be difficult to take action on.  For a service process, I would use DPMO, since a defect in this case is an unsatisfied (not returning) customer, so you would want to measure multiple points to satisfy or dissatisfy that same customer throughout the interaction to pinpoint areas that need attention.
 
Regardless of which method you use, identifying opportunities for improvement needs to be the primary focus, with comparing like processes important but not the most important