FYI, AMD and Intel's OpenGL drivers are below average in comparison to Nvidia ...
While AMD drivers did have issues in RAGE, a lot of OpenGL games run as fast or even better on AMD cards when comparing competing generations.
AMD has good OpenGL drivers for a very long time, in fact since HD5870 and 5770 days:
"OpenGL performance seems to be a strong point for ATi lately, especially in Doom 3 engine games like these two, and it really shows here.
In Quake 4 we see blazing performance with 2xSS, which turns in a faster score than 4xMSAA. We also see 4xSS is faster than 8xMSAA. Delivering over 60 FPS at 1920×1200 while rendering each frame four times is amazing, considering the card only has a 128 bit memory bus with slightly more bandwidth than a 4850."
http://alienbabeltech.com/main/ati-5770-image-quality-analysis/9/
In fact, in OpenGL games like Doom 3, Quake 4 and Enemy Territory: Quake Wars, HD5870 beat GTX470/480 easily.
But since NV was so much superior for a decade, AMD's OpenGL drivers suck meme has stuck around. The reality is far different as AMD cards are very fast in OpenGL.
^ All of these are OpenGL games.
The only thing that's hard to explain is how TPU is getting such horrible performance in Wolfenstein on AMD cars but GameGPU doesn't show this at all.
So when are we going to start calling for blood because the developer didnt optimize for nvidia?
Also 95% of the time NV is indeed faster with OGL. This is why AMD steam boxes make no sense at all atm
Titan X is winning and there is no situation of HD7950 beating GTX980
As far as your 2nd statement goes, AMD has been extremely competitive in OpenGL since HD5870 series. Today NV will outperform AMD since they do have the Titan X and 980 which are faster cards than the 290X but 780Ti can't really beat 290X in OpenGL. AMD's biggest problem was how some openGL games treated texture caching (Rage).
From what I've read, the Old Blood is pretty boring / uneventful game.