The bus “tour” has no sense if nobody explains where you are, what you see. Most of the buses are just that: buses going in circles around the city; hopping on and off we got only once! an amazing driver-tour guide who made the difference, so if you get a driver who is in the right mood and is giving you the tour you paid for, stay in the bus for the whole loop!!! or you could loose your only chance.
Also, the buses are working almost office hours…
I was a big fan of Big Bus Tours, always recommended them, well… not anymore!