Do yourself a favor, stop looking at other listings and book your stay at Eva Und Michi's place! The apartment was perfect for my wife and I, but could easily accommodate a group of 4-6 people. The location was great, my wife is 6 months pregnant and we walked to the city center every day with no problem. It also felt very safe without being right in the middle of too much action.
The apartment was even better than described and was perfect for our needs. There is a mobile wifi hotspot included with the apartment that you can take with you during the day. Had no idea how much we would enjoy this but it was awesome to have.
Michael and Eva were also wonderful. Met us at check in on time and allowed us to leave our bags in their office while we went out on our last day. The airline lost our luggage on the way there and Michael met the delivery truck to pick it up the next day while we were out on the town. It was a very nice gesture and one we appreciated tremendously.
Bottom line - highly recommend for just about any person or group spending time in Vienna.