As a city I like Buenos Aires better than Bogota. Better weather, more things to do, easier to get around, safer, etc.
I'm not a fan of the bigger cities in Colombia. Bogota is ok, but too cold, overcast, bad traffic for long term. Medellin is overrun with gringos and Cali is ok, but nothing note worthy. Cartagena is way too touristy with people constantly trying to hustle you. There are beautiful smaller cities and towns though.
If you're from the US, one of advantage of Colombia is that the flights are cheaper, more frequent and shorter to the US.