Different back test data assistance

[Teck Hua Chew]

Hi, I need some guide on the back test data. I have search thru the forum, there's similar issue, but I still haven't go the understanding that I require.

Should I download the back test data from the broker I am going to trade with? E.g. Download the TickMill MT4, create the demo account, download from the history center.

or Should I download the back test data from metaquote-demo?

As I did the back test on both set of history on the same currency pair. It gives me very different result. So which one is a better guideline for the EA testing?

Thanks!