I may take a medieval arrow in the back for this, but I've been to Rothenburg a couple of times, and the vibe for me was hokey and inauthentic on both occasions, the Nightwatchman tour included. Not that he's not entertaining... he is. But it was hardly the earthshaking experience that might explain the tourist hordes that populate R'burg every day. Medieval torture instruments don't qualify as all that interesting either, IMO. Aside from the outstanding buildings there, which really are captivating, nothing moved me much. The place is just filled with tourists, many of them from my homeland, and the merchants/innkeepers that serve them.
Bamberg OTOH is a living, breathing city historic city where normal German people live, work, and study, not a Disney-village with trinkets that exist only for tourists. Use the Bamberg site in one of the previous posts and you'll find much to see and do. I'm wondering how you chose Bamberg, actually - was it only the Rauchbier? It's a UNESCO World Heritage Site for many reasons.
I'd spend a few hours in Rothenburg. A couple of days in Bamberg might be possible if the stuff there interests you.
The riverfront neighbor-towns of Ochsenfurt, Marktbreit, and Sommerhausen are very worth a stop and not far from Rothenburg. I'm amazed more people don't mention going to these towns. Maybe you'd have time to give them a look in between your other destinations. This rail map shows their relative location to Rothenburg and Würzburg.