I would recommend the apartment, the location is both quiet and surrounded by some fantastic restaurants, cafe's and bars. The flat itself had everything we needed for our stay (including cooking utensils, rapid wifi for video calls and towels).
The only tiny thing we noticed was the water pressure was a little variable in the shower, but everything else was amazing.
Both Alex and Mary were easy to contact and reach out to, and Mary looked after our luggage for a day whilst we explored Athens before our evening flight.
Would 100% come back anytime.