Ease of use? Probably. Better features and performance? Unlikely - ATI's driver (and possibly Nvidia) convert DirectX to OpenGL in the driver itself before execution. See HLSL2GLSL - it's the part of the driver that does the conversion, and is open-source.
DirectX is much much easier if you want to use hardware accelleration. And you do not have to use HLSL for teh pixel and vertex shaders in DirectX. You could write your own machine code for it.