need2know

All I "need2know" is why you didn't use a meaningful subject line.

If you prefer or are more comfortable with OpenGL's C-style API, or if you want cross-platform support.

Well, from what I've seen (and tested) OpenGL is better 'Graphic' wise (it's a graphic engine after all :)) but DirecX has more uses and more managed.

They're both interfaces to the same hardware. Different APIs, different programming paradigm, but more or less the same thing. Choosing which one to use really depends on your goals. By default, OpenGL is my first choice, as long as people continue to use DirectX, Microsoft will maintain their monopoly. That and I develop on Linux :P