Tiles are generally more durable overall. They are less prone to abrasion or scratching. However this is offset by the potentially increased difficulty in finding matching tiles in the event of damage in future years.
Timber floorboards on the other hand (I assume you are intending to polish existing timber floorboards, not install a floating floor) are more prone to scratching, especially by careless tenants dragging furniture across it or walking through the house with stones stuck on the bottom of their shoes. However they can be re-polished, provided they haven't been excessively polished down in the past.
Floorboards should generally be fairly well sealed against accidental spills. Warping or cupping of the timber becomes more of a problem in the event of large leakages or, heaven forbid, flooding, not day to day spillages.
I note that you mention that the property is in Adelaide. If it is an older house with timber floorboards, you want to check that the house is not located on a reactive soils site. If it is, there's a high chance the floor tiles will pop off after a while due to the seasonal movements of the soil.
I have no idea about cost figures, sorry - you'll have to wait for someone else to pitch in on that matter.
