Seeing as you live in Australia, that's a hard one to judge mate given the seasonal differences and weather variety.
You're coming up to winter now right? That would suggest buying studded boots, although it all depends on how much it rains where you live to be honest. If it rains regularly - studs, if it hardly rains - moulds.
The studs won't hurt your feet if it's firm ground but what I would say is it probably increase chances of injury as they aren't likely to go fully into the ground. I've done my ankle for this reason quite a few times. That is only if the ground is extremely firm though.
On the second link you've given there, if you look under technology it gives some quite useful information as to the different soles and what they are made for - You then know what type of boot would be most suitable for you, studs, moulds, blades etc.
As for the price differences, there's always usually 2 to 3 different models of the most popular boots and the price determines the quality of the boot. That means the quality of leather, the heel (which will usually have more support if you pay the higher price) and other bits of 'engineering' with Nike have claimed to have added to the boot.
In my opinion though, there's absolutely no need to spend around £135.00 on a pair of football boots. At the end of the day it doesn't make all of that much difference. Don't forget the players who own boots of these kind of prices are generally sponsored and provided with these boots.
However, I did notice you are looking there in the 'ID' section which means you are customizing the look of the boot - meaning more money. If you look here:
http://store.nike.com/index.jsp?country=GB&lang_locale=en_GB&sitesrc=GBLP%23l=shop,pdp,ctr-inline/cid-300/pid-237103/pgid-228604#l=shop,pwp,c-300/hf-787+4294966803There are some better options, ranging from £35.00 to £60.00. I don't think the £60.00 ones are any different to the £90.00 ones you are looking at there, other than they haven't been customized with Nike ID. There's two pages there, not consisting completely of Total 90 boots, but there is some more choice at least.
To be honest though, I don't think the Nike store is the best place to buy them from, you don't actually get as much choice as other retailers and you are likely to be charged more.
I'm not sure about delivery to Australia from these good retailers but they may be worth a try mate:
http://www.prodirectsoccer.co.uk/speedshop.asp?DEPT=2&BRAND=9&SS=1&PROFILE=Power&ALT=Nike%20-%20Total%2090%20Laser%20II%20-%20Shoot%20-%20Strike%20-%20AZT90Extremely good choice of Total 90's there. If it's not definately Total 90's that you want then it has more or less every other type of boot possible on there.
http://www.jjbsports.com/football/boots/mens?type=1&category=001810004610068&numshow=24&sortnum=1&sortorder=A&pagenum=1The choice there isn't as great but they have all the main models, for a decent price. I noticed a lot of boots there have been reduced too.
However, interestingly:
http://www.jjbsports.com/nike-total-90-strike-ii-fg/prod_161328.aspxAren't they exactly the same as those £135.00 ones from the Nike store? If not exactly the same, I'm telling you now, there is not much difference at all. Not enough difference that would make you want to pay £70.00 more anyway!
Those boots there are blades and I actually think blades may be a good option for you - they will work on damp ground extremely well, really wet ground reasonably well and firm ground well. It's better to have blades on firm ground then studs in my opinion. I only own studded boots because I'm sure you're aware what the weather is like here in Britain!
Hope I helped mate.
