In short: We highly recommend staying with Capitalia!
The apartment is bigger, nicer and more modern than we had expected looking at the pictures. The gym, garden and terrace are great and the staff is kind and attentive. Getting to most touristic places is very easy by using Uber (usually 3-10min waiting time until a car arrives; 30min drive to Six Flags, 30-50min to the city center depending on the traffic; 170-250 pesos). Capitalia provides a great service and will get back to any questions in no time.