Ok stay close to the city center.
Plus sides of the appartment: it is close to everything. Spacious place. Fully equipped. All you can possibly need for a short to medium stay.
Minus: Less positive first impression because of bad air. The place had clearly not been ventilated in a while. The TV is German only. So and so cleaning. Odd bed with what looked like 2 mattresses one on top of the other. Cheap, synthetic linens and pillows.
The nearest subway station is Sudtiroler Platz, just 3 min away at the cross between Weyringergasse and Favoritenstrasse.
25 min walk to Karlsplatz.
10 min walk to Belvedere Palace.