David, thanks for reasking the question. "Effect-on-subject" or quality of light is exactly what I am looking for and I think you previously stated that you have used both and can't tell the difference in that respect. What were you shooting, people or products? I don't often do product type shoots but I can see that a softbox might have more advantages on products than people, like the siliver ornament example that Ed used. But that really is a catchlight shape issue.
So back to the original question, are there advantages to softboxes over shoot-through-translucent-umbrellas other than the catchlight shape and more control of light? Ed says "more even and softer light" which so far is about the only difference mentioned other than light control issues. My impression from Ed's posting is that it isn't a dramatic difference and David says no difference.
Any other opinions?