I feel like show-accuracy is a word irrelevant now. Sure MP10 is the most show accurate Optimus Prime we've had, but if I put it next to say Shockwave or Ironhide, they look aesthetically different. The biggest difference if you ask me? Plain surface vs detailed surface.

Before Kobayashi took over, Hasui would fill all the big robot surface areas with mechanical details. Prime's waist, Datsun brother's shoulders and Bumblebee's forearms are but a few examples. Now you look at Shockwave, Ironhide and Inferno, with huge thigh/leg/forearm areas with minimum detailing, which is to re-create the minimalist approach to drawing the characters in the cartoon.

I reserve the word "dated" to describe the Hasui era figures, as many people pointed out engineering wise there's arguably very little that can be improved on. It's just that they don't fit in with the Kobayashi figures that well.