When picking a city tour it doesn't have to be on a open-top bus with an audio-set. In both Edinburgh and Glasgow there are some pretty cool tours and most have a special theme including special interest tours, history tours, literature tours, abandoned places tours, and even (my favourite) ghost tours.
Underneath the City Chambers in Edinburgh is Mary King's Close which was a street that was abandoned during the plague and encased when they built the Government building above. There are also plenty of ghost tours with Edinburgh having endured the plague, the witch trials and the notorious Burk and Hare. A Royal Edinburgh Ticket includes a bus tour of Edinburgh plus access to Edinburgh Castle.
Most of the tours are humorous and there are also free walking tours in both Edinburgh and Glasgow. It can also be a nice way to meet people in a new city as they are popular with tourists who have just arrived and are trying to get a taste of the city.