Windows Qt with MinGw or Visual Studios?

MinGW uses GCC, and GCC has one significant advantage to MSVC - it is portable. MSVC is limited to Microsoft platforms, GCC supports pretty much everything, including 8bit embedded CPUs. Meaning that you can use the same directives and compile extensions across different platforms.

Also, MinGW is compact, quick to install, and a version is even bundled with Qt. Unlike MSVC, which is not even available standalone, you have to install visual studio, which itself installs a bunch of garbage you don't need but can't opt out of.

UPDATE It is now possible to get the MS compiler without VS, a.k.a MS Build Tools. Also, If you want to build chromium (a.k.a the QtWebEngine) for windows you have to use MSVC, that's a limitation imposed by google, as they only support building with the platform-native compiler.

Last but not least, you can get MSYS2, which has a repository with MinGW and a ton of ready to use static and dynamic libraries build for it, so you can avoid the arduous and often failure prone build process.

UPDATE Just for the sake of reference, for VS build tools 2019, the C++ compiler alone takes up about 4.5 gigabytes of space, or about 8 if you just click "C++ build tools" and leave it at the default. For comparison, GCC 9.x is about 150 mb. In fact, the MSVC compiler alone is larger than the entire extensive collection of packages that I adopted for use throughout the years, plus their dependencies, for a total of over 200 packages. Additionally, I'd say MSYS had packages for about 98% of the libraries and tools I've found myself in need of, and those remaining 2% include libraries it had but were not configured in a way, suitable for my use case. And it goes without saying, the packet manager makes it trivial to keep versions up to date.

They are both fine tools. The important thing to know is that they don't necessarily play well together. That is, as you link libraries together, they must all use the same tool chain. For this reason, in my opinion, it is better to use the Visual Studio compiler (MSVC), as it is the "first class citizen" on Windows; the others are treated somewhat as second class.

What I mean is that you can pretty much count on third party libraries being available in binary form using MSVC, or at least build instructions being available using MSVC. We had lots of problems with third-party libraries not being able to build in MinGW or having nonexistent build instructions and having to do a lot of manual Makefile editing, etc. You are much more likely to have things "just work" if using MSVC.

That is just our experience (we started with MinGW); your mileage may vary.