The speed-features I mentioned are valid for Direct3D as well, no worries
(since these are features in Hardware, not OpenGL specificly). BUT:
"Crossplatform" wasn't important to me either some time ago. However things changed:
Future versions of DirectX won't be able to run on any 'serious' Windows
anymore but Vista only. So you either exclude all non-Vista users with your
decision or freeze with DirectX 9.0 (remember: DirectX, in opposite to OpenGL,
is NOT extendible by HW-manufacturers).

DGLOpenGL is a nice header because you don't need to deal with
Extensions seperately - they are included. Also the initialization is a
piece of cake. Its not a complete framework or engine - its just a
way of directly accessing OpenGL (which gives you an extra of control).

The choice is upon yours. But I *strongly* recommend OpenGL or
some OpenGL-based engine.