Obviously every city has its tourist attraction, if you have to choose between Medellin or Bogota, would be Medellin because it has places that call more attention, I visit a while ago and if you plan to go I recommend using the page Yoplan.com as if you're going to Bogota. And in the case of Lima or Quito, I think it is better Quito, because you can do a lot in Quito instead of Lima.