Between those two, the dell is better. What you should do is see if you could get the HP dv8t Quad Edition. The recomended config has the same specs as the dell, has an 18.4" screen, and costs $1,729 USD 1,919.83 AUD. I didn't see it on the HP australia site, but here's the link.
http://www.shopping.hp.com/webapp/shopping/computer_can_series.do?storeName=computer_store&category=notebooks&a1=Category&v1=High+performance&series_name=dv8tqe_series&jumpid=in_R329_prodexp/hhoslp/psg/notebooks/High_performance/dv8tqe_series
Good luck with your search
On second thought, you have the option of Alienware.
the M15x for about $2000 USD gets you a nice boost in Video cards
Intel® Core™ i7-720QM Quad Core Processor 1.6GHz (2.8GHz Turbo Mode, 6MB Cache)
1 Year Basic Service Plan
1GB NVIDIA® GeForce® GTX 260M
15.6-inch WideFHD 1920x1080 (1080p) WLED
6GB DDR3 at 1333MHz
320GB SATAII 7,200RPM