One of them has a walking tour of the Albaicin neighborhood (former Jewish quarter), the other one just drops you off for a couple hours to wander around while others are doing the tour. By the end of the day, I was kind of tour-ed out, but Albaicin is very cool. And there’s a park on a hill that lets you get the wide-angle postcard photo of the Alhambra. You don’t get that if you don’t do the extra tour. The bus drops people off at the bottom of a hill and then drives up the hill into Albaicin. So if you wanted to do a lot of walking, you might be able to do it on your own. But you don’t actually get a lot of time for that, so it might not be worth the risk.