about direct3d and opengl

I want to learn the difference between openGL and Direct3D…

From the user’s point of view, there’s little difference, I mean, games will work virtually the same with any of the two (if the game can use any of two APIs).
More generally (still for end users):

-Is controled by a single company (Microsoft, which by the way has the reputation of wanting to control everything it can)
-Works only on windows95, 98, Me and 2000 (no NT 4.0 since DirectX3, a long time ago).
-Each time a new version is released, you have to download it and install it (it cannot be uninstalled).
-Drivers are installed appart from the DireceX8 installer.

-Is controled by an independent, multi-company review board (where a lot of people participate, including Microsoft)
-Works in almost all OSs (linux, all windows, MacOS, BeOS, irix, unix, etc).
-Video card vendors implement OpenGL in their drivers, so improvements done to OpenGL will automatically reflected in new drivers you download.

If I understand that correctly OpenGL replaces DirectX on an NT machine? Meaning just because I can’t install any DirectX on it still would allow new games to run because of OpenGL?

Oh in addition maybe someone could tell me what I should use if I can choose from DirectX, OpenGL and Glide. What would give me the best performance?

I have a Voodoo3 2000 on an NT(SP6a) machine

glide is 3dfx native api and will only work on there video boards
glide was easy to write for and ran very well but it is getting a bit old in the tooth.
direct x was invented by microsoft for programmers so they would be able to take control of the systems hardware off windows and there for make it easier for write games on the windows platform it has several parts to it directdraw,drirect3d,directsound,directinput,and a few other parts as well.
it is also meant to be a allround 3d renderer ie: if i wanted to play unreal on my tnt card even though it didnt support glide i could play it in direct3d mode,
although it didnt look or run as well as with glide i was still able to have hardware acceleration.
directX3 was okay and as they continued they got to the final release knowen as directX8.a witch will be used in the X-box console game programmers to use for there games.
and as for games try to choose the rendering api the programmer designed the game for
ie:quake123 use open gl as there are the only ones they support in your case the 3dfxminigl driver for say unreal rollcage and deus ex you should choose glide because you r usng a voodoo i even think that that duke nukem forever will support glide
(i think)were as the rest of us will have to use the direct x instead

ohh yehh
diffrent renders do make a lot if diffrence look at half-life in d3d then in open gl and you will see not to mention rollcage or unreal and the diffrence over glide
and i forgot to mention there are games that run only on d3d too just take a look at system shock 2 or 3dmark2000 20001 and 99max