This seems to be a bug, because on Qt Creator, Q_ASSERT(false) causes my application to quit even though the documentation says it should allow you to break at the assertion:
On Windows, for debug builds, this function will report a _CRT_ERROR
enabling you to connect a debugger to the application.
On Qt Creator:
When compiling my project in Qt Creator+MinGW, the code Q_ASSERT(false); causes the program to display this message (screenshot below), after which the application quits:
This application has requested the Runtime to terminate it in an
unusual way. Please contact the application’s support team for more
information.

and Application Output pane shows this debug output:
ASSERT: "false" in file ..\IntegrateWithQt\main.cpp, line 6
Invalid parameter passed to C runtime function.
Invalid parameter passed to C runtime function.
On Visual Studio:
When compiling the same project using Visual Studio (I import it with the Qt Addin), I get a much more useful Abort/Retry/Ignore dialog, where clicking Retry breaks the program at the location of the assert:

The version of Qt I link to both in Qt Creator and in Visual Studio is 4.8.1. Both projects are built in Debug mode.
So how do I get Qt Creator to allow me to break at the line of the assertion in debug mode?
My guess is that you are using Mingw in Qt Creator and MSVC (obviously) in Visual studio. Different compilers produce different code.
Try using MSVC in Creator (you will need to get a Qt version that was built with that compiler to do that!) and see whether there still are differences.