First was Above and Beyond (1952) and then The Dam Busters (1955). The first was about the Enola Gay and the run on Hiroshima, the latter about taking out German dams with an innovative "skipping stone" five-ton bomb which would get spent along the edge of the dam, fall down thirty or more feet, detonate, and use the reflection of the water blast to punch out the dam.
The obvious similarity is that both missions require a specially trained unit and a very special weapon. And both are WWII movies. After that, the differences are considerable.
The US Army Air Corps B-29 Superfortress was a high performance, high altitude, pressurized cabin bomber. It required reinforced concrete runways at an isolated island base at Titian. And the uranium fission bomb required care, radar altimeters and crew safety precautions.
The British Lancaster bomber also had four engines, but had an unpressurized box fuselage and used grass landing fields in England. Their bomb required low flight, with altitude determined by a crossed floodlight system and a simple Y-shaped bombsight.
The Hiroshima bomb was a one-off. The other planes flying that day were weather and camera planes. Indeed, a lone B-29 flying weather patrol was not considered a threat and so they were not fired upon. The dam busting bombs were used in multiple planes over multiple targets on their one mission. They were subject to ground attacks and lost several planes.
And then there's this. Part of the reason for making Above and Beyond was to show the strains on marriages in the young Air Force. To try to show that this was a necessary job, despite the secrets and the away time. As for the Brits, there's a glaring bit of controversy about the name of the black dog who served as the units' mascot -- being a black dog he was called "Nigger", a word I thought I'd never have to type in this blog or hear being uttered as a term of endearment by the white British flight crews. Certain prints for television have the dog's name either censored or redubbed as "Trigger".
Wikipedia mentions that Peter Jackson is working on a remake of The Dam Busters. They may use the actual alternate nickname of "Nigsy" for the dog -- under the theory that they are damned if they do and damned if they don't over historical accuracy versus offensive language in 2009. The Wikipedia article also points out that the attack on the Death Star in Star Wars, i.e. the original which is now Episode 4, is based on The Dam Busters.
An interesting pair of movies -- the sterile high performance of the Americans versus the gutsy lower tech British "Cook me a kipper, I'll be back in the morning" fliers.