You cant for this reason: on each of this "systems" different things are going on.
If you wanted to do a real benchmark, you'll go with equal code for GL and DX. all by your own, with no third-party libraries (bloat-adders in this case).
Thats why I say "you can't" because its pointless in the current form to do a benchmark.
As for a "user" benchmark, where you want to see whats faster for your program with what you are given (the sprite lib and the ogl context)... Okey then, go on.
But as people keeps comparing DX with OGL, I keep on getting mad!
We'll see with upcoming crossplatform DX builds how good it performs against OGL... I wouldnt, anyway, move to DX unless I have more than a real cause. Yes, I'm all comfy and warm since a long time with OGL, any problems?
As for the real discussion: DarkDragon more likely means that you cant compare "PB" with OpenGL! because its a very -very- stupid comparison, PB is NOT a graphics rendering context, its not at all that. PB's sprite3d lib: It's just wrapping a few DX calls and thats about it. No heros required for that, no mysteries.
It might work better for you, but you wont get crossplatform.
Even if you save 10 or 20fps, you'll still get no crossplatform.
Even if you didnt want crossplatform, you wont ever get it with the current DX version that is being used..!
HA!
There aint much to code about sprites... You just need an eye view matrix, and perform your billboarding calculations... As for each "sprite", graphically talking its just a quad (2 tris). You can already do this on your GPU for saving some of this calculations (if not all of them

on some cases)... But still, your comparison is a null to me!
Also: you're using a non power of 2 texture....
If you're going to use your own OGL context, this translates to: you will have to resample the image (most engines does a nearest power of 2 call, then they super-sample the image, the result is a blurry image that might be taking more ram that you ever needed or wanted).
OGL wont do it for you as far as I know.
Also if you're about to make a benchmark... dont use any type of text displaying.. Just run a test for XX seconds with a set amount of objects being displayed, stop it and get to measure the time it took to render an X amount of frames....
The graphical output is totally different from each test, this is no way a valid benchmark.. Anyway I get the same speed results (in your poor fps counter). However it depends a lot on the gpu, if it was optimized for OGL or DX, the drivers mosty, etc.