Which way to travel around this big Island is something of an interesting debate.
Here are a few of the factors to consider:
It is unlikely that you when planning your trip you are thinking about the Wind, but it is a worth a look into. Travelling head first into wind will make it self well known when filling up, as will having the wind behind pushing you along, only the latter will put a smile on your face, the former will only make you cringe. This is especially true if you are towing a van.
To ensure more time is spent driving with the wind, and not in to it, an anti-clockwise direction is recommended.
Side of the Road
It is said that by travelling Anti-Clockwise your cover less distance as you are on the inside lane. Though this may be so, I am not sure you should base your whole trip on this fact alone as the difference is minor.
Time of the Year
I personally think this is the most important factor to consider. Depending on the season a good guide is to head North of the Tropic of Capricorn for the Winter and spend the Summer months South of it. As the Wet season makes the North virtually inaccessible and can be pretty unpleasant, meanwhile the South thrives in the Summer times!
and I am saving this for last,
I think personally if you keep the last point in mind, when considering the North, heading in either direction will be just as good as the other.
Currently our plans are to do a bit of a figure 8 which will mean we experience a little of both directions. We plan to head Clockwise along the bottom to Perth, up the coast making our way to Darwin via the Gibb River Road and then Down the Centre, then up along the East coast. After that, who knows? maybe we will do another lap!