There are two places in Visual Studio project settings where include directories can be specified:
[Configuration Properties] > [VC++ Directories] > [Include Directories]
[Configuration Properties] > [C/C++] > [General] > [Additional Include Directories]

When Qt modules are selected the add-in currently uses second location.
It would be useful to be able to select which location is used.

Background for this suggestion:
Recently a popular VS plugin Visual Assist X added a support for Qt5 headers in their feature that inserts include statement for unknown symbols.
The feature is very useful, but with the current Qt add-in behavior it adds eg. "QByteArray" instead of <QByteArray>.
The selection of "" or <> is based on the mentioned location of headers.
The first setting is generally considered "system wide" location, so it uses <> syntax.
The second one is considered "project local" location and uses "".
Qt is usually installed separately, so it should rather use first location or give user a choice.