I have a question that has been troubling me.

Where does your data for backtesting come from? And, does it accurately reflect other market data sources?

The reason I'm asking is that I've been experiencing a competitor of yours system, and I found some serious issues with there data not matching other data sources such as Yahoo and Google (plus others!). Is data for Quantconnect better?

I need to know before I switch direction and learn C#!

Thanks for any help you can give me.