mjh:Bowmouth, without a doubt PNG and Koa Samui are very different locations but that is way you can compare and contrast them. If you are someone in the middle of Kansas, Germany or Uzbekistan, that may have never traveled outside of the country before, you may find the comparison between the two helpful.
Personally I'm still all for just describing different dive sites in a no-nonsense way and pointing out the highs and lows of each individual dive site rather than stating "this is better than that".