More modern programming interface that matches the hardware better. Newer shader model support + newer shader compiler Newer/more powerful debugging tools Ac

More modern programming interface that matches the hardware better. Newer shader model support + newer shader compiler Newer/more powerful debugging tools Access to large new features like compute shaders, texture arrays, uniform buffers, etc Access to new surface formats to enable features like VR and HDR Better API performance + access to performance-enabling features like multi-threading Direct3D 9 is nearly 20 years old. OpenGL has at least been receiving new extensions on a regular basis (though people are finally shifting to Vulkan) - with the exception of a few things shoved in by driver vendors via back doors, D3D9 has not changed at all. Driver compatibility for D3D9 is also very bad at this point - the driver vendors don't give a shit about breaking existing software that uses it. I still occasionally hit driver bugs when working on old code that targets 9. Code targeting 11 will have fewer problems.