The Defender and Islander are very different animals-the Defender or Defender 4000 to give it it`s full title,has quite a few modifications to the airframe.
The BN2 Islanders used by the AAC and Police are much more like the civvie type Islander except for all the goodies they have inside.
I think you will see the Defender version becoming a more common site at Aldergrove as I hear 2 more airframes for the AAC are on there way soon.