Both countries are really beautiful.
At the sane time they are different. Colombia is quite a safe country, I have been there several times and I am actually going back in one month. It is really beautiful and there is a lot to see and to do.
Argentina in the other hand isn one of the most beautiful countries of the world. Now is winter over there and a nice time if one like winter sports.
Bot places are worth a visit. Tourism is more develop in Argentina so it is easier to go around but everything is fine in colombia as well.
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