Personally, as a Western suburbs resident, I'd be really cautious about investing in the outer Western suburbs, as I would outer East such as Pakenham, Narrewarren, etc. My feeling is that if the market flattens out or even dives, these suburbs will be hardest hit.
When researching an area, I like to look at the data for as far back as I can get. For example, Taylors Lakes price didn't move at all for 6 years between 1991 and 1996 before taking off. However, everywhere in Melbourne has grown in the last four years so the fact that it did is not much recommendation to me. I am looking for suburbs which do okay even in the tough times, not just in the booms. I would much rather buy into a suburb whose price increased even marginally during a lull in the market.
If you wait a little, you may find prices in outer suburbs return close to 96 levels, which would be a much better time to buy.
Also I don't think that those suburbs have much to recommend them to tenants. There is too much property that is too similar and they tend to be less well serviced by amenities. There is no reason why a tenant would chose your property over many other similar properties. In fact they will tend to go for the newest one, especially now when the market is overstocked.
I am more optomistic about Werribee, but I would really want to check out the state of the rental market there: what the returns are, what tenants want, vacancy rates etc.
I know this sounds really pessimistic. I guess what I am really saying is
do your research! Make sure you know the area well, the rental returns and how it fits into your strategy. Don't just buy because it is cheap and sounds like a good idea. If you do, it might come back to bite you on the bum!
All the best,
Sue