One more data point- Went to Hiroshima/Miyajima in 2000, Nagasaki in 2005.
If you are going to both cities, I'd prioritize the Nagasaki Peace Museum, as I think it is much better overall. For Hiroshima, I'd make sure to walk by the A-bomb Dome, the Cenotaph area, and, time permitting, visit the artifact area of the Peace Museum to see the stopped clocks, melted objects, and the "shadow" on the bank steps, as these are the most visually and emotionally striking parts of the museum, IMO.
I might have written this on one of your previous threads, but Nagasaki is a great city- there is so much to see. I'd limit Hiroshima time to a quick walk through and maximize Miyajima and Nagasaki time.