You're right, the methodology is similar, just for different goals. That one is trying to figure out which picture to use for your profile, whereas this app is trying to help you in making every-day decisions such as what to wear or what to buy. A key element is the response time -- I'm not sure how fast this service gets you an answer but I'm assuming it's not within seconds.
The idea as I presented it would require a certain amount of traction to get started. It only would take about a second to look at two photos and tap one, so assuming 30+ people are using it at any given moment, you could get 30 votes within 30 seconds.
