Imagine if instead of the Death Star, Darth Vader imprisoned Princess Leia in Cloud City. It's a difficult idea to wrap your head around, but that was the case in an early draft of Star Wars: A New Hope. In that version, Luke Skywalker rescued the princess from the Imperial City of Alderaan, the capital of the Empire, a location that ended up inspiring Cloud City in The Empire Strikes Back.
The Death Star may seem like a vastly different setting from Cloud City, but Ralph McQuarrie's initial concept art for the Imperial capital is a little different from its final design. While it's still a city suspended above a gas planet surrounded by clouds, the structure is more dome-like. In addition, the different levels are quite pronounced on the exterior and more varied in style. The city itself doesn't look too menacing, but the surrounding grey clouds give it a slightly ominous feel. Even so, it would've made for a very different backdrop for the iconic escape sequence.
Elements of the original Cloud City may have even inspired parts of the Death Star. Instead of a dome, the Death Star is a sphere, and like the original design for the city, its surface is full of trenches. McQuarrie also painted the Millenium Falcon docked in a hangar in the city, which he later revised for the Death Star. While the hangar's design continued to evolve, these paintings would later inspire the opening shots of The Phantom Menace. Although these may not have been the final designs for Cloud City, they clearly had an influence on the look of more than one location in the galaxy.
When the design returned in The Empire Strikes back, Cloud City became much sleeker. McQuarrie revised the design and made the structure smoother and rounder. The lack of rough edges gives it a softer but still futuristic feel. He also emphasized the domed buildings on tops of the city and painted it against a bright yellow sky, making it look warm and inviting. Eventually, the entire city was flattened and widened into a smooth, saucer shape and the supporting beam underneath became skinnier. While one might question the structural integrity of the final design, it gives the city an almost ethereal look.
As one can see, the final design for Cloud City reflects its new place in the Star Wars universe. When it was originally designed as an Imperial city, it was cold and jagged. It wasn't quite as intimidating as the Death Star, but it was much more aligned with the Imperial aesthetic. As its place in the story changed, however, the design became softer and more inviting. Still, the beautiful city hides some dark passages, which demonstrated its new role in the story as a place of refuge that turns out to be a trap. Nevertheless, the city is ultimately against the Empire and its final design reflects that.
While the Imperial city of Alderaan would've surely been an interesting setting for Star Wars' first rescue mission, the planet-killing Death Star is just slightly more fitting for the menacing Empire than a city in the clouds.