Not sure about the feature comparison of Direct X and OpenGL.
What we have experienced is....
Direct X Platforms
PC
XBOX
XBOX 360
Zune (?)
OpenGL Platforms
PC
PS2
PS3
PSP
Nintendo DS
Nintendo Wii
Mac
iPhone
Now it becomes a developers preference as to where they want to spend their time and energy.
Direct X is very Microsoft Centric, OpenGL offers more platform choice.
Since the main open systems for Indies is the PC, Mac, and now the iPhone. It really is a toss-up....
Agreed that most hobbiest's buying a $200 3D engine will have PC's and not Mac's. That definetly is the market 3DGS is going for, I am not so sure about Unity. Seems to me Unity is doing a good job finding biz other than the Window Hobbiest's.
Windows 3D engine land has many competitors. Bigger Pie, lot's more pigs eating at the troff...
Ken