Comparison between XNA and DirectX (C#)
In terms of PC development (excluding Xbox and Zune),
What is the difference between XNA and C# DirectX? Does C# DirectX have a significant advantage over XNA (in terms of speed, royalties, etc)?
How are the two compared to the speed unmanaged C++ DirectX?
Where is the industry moving in terms of game programming?
Answer
If you're actually good at writing unmanaged code, then you'll probably be able to write a faster graphics engine on top of DirectX. However, for the hobbyist, XNA has plenty of performance, both for 2D and 3D game development.
Here is a good Channel 9 video where they run an XNA-built racing game on Xbox 360. It runs well even at full HD. Several of the XBox Live Arcade games have been developed by the XNA community.
As far as C# DirectX, as I recall, Managed DirectX as it was called, is no longer officially supported since XNA basically replaces it. I could be wrong, its been a very long time since I looked at it.
The performance differences are negligible between XNA and Managed DirectX since, in essence they're the same thing; XNA just has a few convenience bits to reduce the amount of boilerplate code you need to write.