The Master Touch is worth the extra money, it comes with accessories you'll likely buy anyways. My Master Touch was the first grill I ever bought and my 2nd kettle, it is currently the work horse.
The 26" is a good size, I have found my 22" to get a little crowded when cooking multiple shoulders and ribs. However, I still use my little 18" frequently. In hindsight I would have gotten the 26".
I currently have 6 Kettles, It's nice to have a quiver to choose from
I just looked at the Weber Australia page, the Master Touch you get is different from what we have availible here in the USA. I really like the additional features, especially the wheels. I wonder what it would cost to ship a Weber from Australia.......