SierraChart is very particular software. It is made by fanatics coders that are obsessed with performance and features.
As I first started using the software, I found something missing and I made a suggestion.
The NEXT DAY, it was implemented, and available in the next release by the end of week.
So here I was a total newbie, influencing the development of that huge software. To this day there is a setting checkbox in the software that originated from one of my remark.
They are constantly adding feature and refinements to their products, with almost weekly releases if not more. Same for their documentation.... if something isn't clear, they will update it on the fly. You won't find any company like this.
Also they have a very distinct advantage: they became data vendor with their own hardware. And order routing. And there are talks that they will create their exchange.
Example of one advantage: they have servers in Europe with direct connectivity to Eurex. Huge advantage for european based traders. Did you know, that with rithmic for instance, even if you choose the frankfurt server, the data goes all the way to the US, then back to europe?
All in all from my experience in using both. SierraChart is better in most aspects, in particular performance and stability. Oh and it is written in C++ and fully supports the entire language for your own developments.
Sierra supports very advanced and reliable autotrading.
HOWEVER, there are some things Ninja does better: the entire backtesting and optimization stack (you can't even optimize in sierra). And that can be a big deal for some. Even for me. Also coding support is better in ninja forums where staff on Ninja will answer your questions directly.