Using Qt 4 vs Qt 5 to develop application for Windows and OS X?
Based just on your platform constraints you probably want to use Qt 5. Windows 7 64-bit is a tier 1 platform in Qt 5. Windows 8 isn't even a tier 2 platform in Qt 4. Qt 5 has better support for High DPI displays (important to Mac users with Retina displays).
- Qt 4 Supported Platforms
- Qt 5 Supported Platforms