No, please don't provide false info.
Based on early benchmark of HD 5100, it's a class 3 graphic card. A little weaker than AMD HD 8670D. And that card runs Sim City at medium settings at 23 fps (pretty low). Given that Sim City for Mac is not as optimised as it is on Windows, I say you'll get 15 fps at max. At medium settings. So no, get 15" please for higher than medium settings.