If you are going to make a game in home, neither Direct3DIM nor OpenGl are good choices. These API requires huge time to make a 3d engine. For example, both are low level API, so no animation import capability ready to use. You may NEVER finish making a 3d game from Direct3DIM/GL.

If you want to finish making 3d game, your reasonable choices will be

a: use free or commercial game engine

b: use Retained mode to make an engine, and port it to fahrenheit (DirectX 8) later for speed enhancement

(Retained mode uses the same 3d draw method as IM, so it is not slow until T&L becomes popular.)