You don't need to pick one or the other. i3wm being a window manager, not a fully fledged desktop environment, means you can use it with KDE or Gnome for example.
I have gone down that route before too, several times, it is not pretty. The KDE panel and startup splash screen don't play nice with a custom WM. Removing the KDE panel also removes a lot of the kitchen sink functionality I was looking for. The best option for tiling in KDE was using a KWM extension that supported it.