which should I see if I only have time for one?
As a tourist for a day I would say either one. Everything else, Regensburg. If I had to compare one to Disneyland, it would be Rothenburg.
I like both. I would pick the one that fits your travel route best or is the closest day trip.
I have been to both a couple of times and both are a great visit. You can do most of what you want for both in one full day, while Regensburg could use a little more.
Don't miss the 1000 year old bridge in Regensburg and the small restaurant next to the bridge that operates from the small building that goes back to the building of the bridge.
Rothenburg is one of those rare medieval walled towns that you can find in Europe, if I had to pick one, it would be Rothenburg.
Also, if you are in Belgium, go to Brugges, in SE France St. Paul de Vence, in Spain, Segovia.
Whichever is closer. They are very different; RodT is the main tourist attraction and kept pretty for that reason, and (IMHO) best before 10am and after 7pm. Regensburg is less touristy, and the old town area is a bit more compact, but it's a much bigger city and there's more to do.
Piggy backing on the original poster's question, I am going to be in Regensburg for a concert in July at the Schlossfestspiele.
Does anyone have hotel recommendations or a suggested area you would recommend I stay?
When? I'm a fan of Rothenburg, and last year, we were there two weeks after Easter. It was peaceful with few tourists. Apparently the weeks surrounding Easter had been packed.
And - the Night Watchman tour is Rothenburg.
In Regensburg, we stayed in the Hotel Orphee in the Old Town, has a 1920's French theme, room was nicely decorated with a very modern bathroom. I believe I used Chase Sapphire points.
Have a great trip!
We like the Weidenhof Hotel in Regensburg. It is in the Pedestrian Zone, about 3 blocks from the train station. Nice rooms, good breakfast and a friendly staff.
It is easier to get answers if you start your own thread.
My favorite place to stay in Regensburg is the Hotel Orphée. The Grosses or Kleines Haus. I've never stayed in the Andreasstadel.