I'd pick the native toolkit for wherever I want to use it. If I want it on Windows, I'd use C++ & Win32 / WinRT. On mac, Swift + AppKit. For iOS, Swift + UIKit

I'd pick the native toolkit for wherever I want to use it. If I want it on Windows, I'd use C++ & Win32 / WinRT. On mac, Swift + AppKit. For iOS, Swift + UIKit. For Linux, probably C and GTK (I mostly use Gnome-based distros). I'd go 100% native because that's how you make the best app for that platform. I also enjoy working with different toolkits and if I wanted this on more than one platform, I think I would enjoy designing and building it for different environments. For example the version I'd make for my small screen touch-based phone would probably be significantly different than what I'd want on my keyboard and mouse equipped big screen desktop. A multi-platform or web-based solution would have too many compromises.