Dents happen when I didn't see something and backed into it, or someone/something else hit the trailer. Dents, in these situations would happen to any trailer you purchase. They may be more money to fix, but not more "dent prone".
Scratches are the price you pay for the beautiful aluminum bodies. Looking at a tree branch sideways will scratch your trailer. It won't be a big scratch and you'll only notice it in certain light. But I do believe Airstreams are more "scratch prone."
Leaks, in newer Airstreams, seem to be from penetrations in the body after the panels have been put together. In other words, the panels themselves don't usually leak. And in 2017, a model improvement I noticed recently on the forums, was a single sheet for the roof. Though I'm not sure how they would do the front and rear caps.
That leaves penetrations such as the AC, lights, fans, antenna, etc. those are what leak because they rely on sealants that either wear out or were never installed correctly. All trailers deal with this.