The re-cuts are definitely an improvement on the original theatrical release. It's a matter of taste, but for me Director's Cut is the better.

I wonder if part of that is that Blade Runner doesn't optimize for the first viewing. Once you already know where the plot is going, your attention is free to wander into the production design, sound, background activity

Yup. It's one of those weird and rare movies that grows on you the number of times you watch it. I have watched it at different ages. The later I have watched the better it seemed.