I love Stern and almost all their newer games, but, while they may excel at Lean manufacturing, B/W did have better engineering.
I re-watched the making of video for X-men recently, and they had an engineer commenting on how much time was spent on the design reiterations of the Wolverine figure. I felt bad for that guy after seeing that. Even acknowledging that hindsight is 20/20, it doesn't take an engineer to understand that a flying steel ball colliding with a piece of hollow plastic will destroy It.
That being said, being over engineered isn't the best either. Over engineering just means spending more money than necessary to get the job done. It's easy to over engineer yourself out of business. Bally/Williams did have a great balance.