I don't know lender policy for the small banks not on my panel very well - but take a look at Newcastle lender too - they have some very good rates going on.
As emailed and explained by others here, there may be more to consider than just rate though. If your goal in property is this one and only transaction, loans.com.au (and the like) are a decent option.
NAB is an excellent lender however its the type of lender I would recommend towards the end of one's portfolio when servicing becomes a concern.
NAB (like some lenders) calculate other lenders' loan repayments at actual repayment amounts (i.e .the interest only amounts) whereas NAB calculates their own debts at what is called "benchmark" rates of 7.40%. This is huge. So you don't want to peak too early with NAB.
If you are going to buy one property then all good but if you want to build a portfolio then I would use only when you need to.
On the other side of the coin - you don't want to use a lender that is overly conservative which will stop you from going back and doing an equity release.
The other thing I would recommend you consider is the LVR. Based on your future plans - do you do the purchase at 80%, 88%, 90% or 95% LVR?