Neither is better. This is a stupid question that has been debated many times in the Game programming section. Anyone that says Direct3D is better than OpenGL or vice versa doesn't know what they are talking about. It it purely a matter of preference (unless you are targeting a platform other than Windows in which case OpenGL is your only choice).
Most games use the same format:
OpenGL doesn't seem to cause the CPU to max out when running
This is why the CPU gets maxed out, it has nothing to do with the graphics API.