Ultimately every loan is assessed on an individual basis, generally speaking though a first home buyer is riskier than an investor though. Especially if you were looking at a first home buyer wanting a high LVR loan. They generally have no proven savings ability so unless they have been a long term renter you have little evidence to show they are able to put away $Xxx regularly for repayments.
An investor is more likely to have additional properties that can be used as additional collateral. Of course the investor could be highly leveraged against many properties hence the comment that every deal is assessed on an individual basis. If you look at the last downturn/flatline in Sydney (GFC) it was mainly first home buyers/owner occupied people that were worst effected. If rising unemployment is the driving factor behind the price falls then it impacts owner occupied dwellings more.
While I work in Sydney, we are a national lender. Post code restrictions are as much for rural towns as they are for inner city suburbs with a large volume of high density apartments. Any suburb where the average time to sell a dwelling takes 6-12+months is going to increase the risk profile because if someone cannot repay the debt the bank is left holding the asset for an undesirable period of time without a fire sale.
