The thing you r telling about

"but you can't run gnome apps on KDE very well.
However, you can run
KDE apps on gnome very well"

Its not like that. Actually, If on Gnome you are
installing anything i.e. any application even a single
music player like AmaroK etc. of KDE then you have to
install all libraries of KDE in Gnome. And same for
the KDE also if you are installing Gnome apps on KDE
then you have to install that library along with that,
which is not recommended. So usually try to use Gnome
application with gnome only and KDE apps with KDE
only.