WA car: As this is a vspec (check the vins to confirm this) this would account for the some of the price difference. An engine compression test is a must. I would also get a paint thickness test done to check for accident history and to ensure it is an orginal midnight purple (also attracts a slight premium).
Vic car: I would be flying over to look at this or at the very least getting an idependent mechanic to look it over. Again compression test, paint thickness test and vins check are a must.
Both cars have nismo aftermarket dashes, so the advertised km's are probally dodgey. I would be looking for edvidence of the 100,000km service (e.g. timing belt) on both cars - if not, get it done asap on purchase. The wa car has been in australia a while, so recent service history is documented which is also a bonus.
It will cost ~$1000+ to transport the car over to perth, but will be pretty easy (no pits required by memory) and cheap to get the rego changed over.
IMHO i would be leaning towards the WA car, just for convinience. However, both cars look good, but i would be pricing the actually cost of buying the interstate car (e.g. transport, flight, mechanics, rego etc) before making a deceision.