If time was not a concern, and if your goal was to maximize image quality, what would be the best practice for moving images from LR3 to 4?

You do understand you don’t actually move images? You just open your catalogue in LR. Images processed in LR3 will still have LR3 adjustments and a little exclamation mark which you click if you want to update their adjustments to LR4’s “process version 2012”. But you can leave the existing images as they are in “process version 2010”. I would do this in general, leaving them as they are, and just update specific images – eg those which might benefit from better treatment of highlight recovery. Meanwhile, become familiar with the new adjustments by processing new images.