AllInTitle for Regional Google Sites

[lotuslight]

Hi,
I'm based in Australia and primarily use the .com.au version of google for my search. I'm currently doing a competition analysis for few keywords and was a bit confused with my findings. For simplicity, I'll use an allintitle search that I did for my keyword: helical rotor pump. My findings:

1. When I did this search on google.com the allintitle:helical rotor pump returned 548 results and an overall broad search of 362,000 results.

2. Next when I did this search on google.com.au the allintitle:helical rotor pump ALSO returned 548 results and an overall broad search of 362,000 results.

3. When I clicked on 'Advanced Search' on google.com.au and then under "Date, usage rights, numeric range, and more" section changed the region to Australia and ran the same AIT search it came back with 83 results and a broad search of 10,200 results.

So my questions are:
1. Why isn't there any difference in the results when I'm changing from .com to .com.au?

2. Which is more accurate result if I'm trying to assess competition for this keyword?

Any guidance would be greatly appreciated.

Thanks,
MT