Ironically HD7970GE is better in OpenGL games than GK104. Many older games are OpenGL games. As far as Far Cry goes, what issues did you have with AMD cards? The weak performance in FC titles was attributed to HD4870/4890 series, especially Far Cry 2. That has been fixed a long time ago with HD5870 and forward.
You didn't mention what happens to NV's performance in "games no one plays". What I mean is less popular games in your Stream library. On the driver side, the argument would be a lot more valid for NV if their cards actually performed well in random games "no one plays". The opposite is true. NV's cards lose badly in non-AAA games. Why is that?
Far Cry 3 Blood Dragon
Dark
HL Black Mesa
Carrier Command
The Incredible Adventures of Van Helsing
Dead Island Raptide
Neverwiner Dungeons & Dragons
Warframe
Firefall
AMD's 7970GE continues to outperform 680 without any trouble outside of the most popular games and by large margins. That tells me NV primaril spends their time focusing on the most popular games while AMD's drivers are more consistent overall. What happens if I want to play a game no one heard about? It gives me more comfort that AMD's 7970GE will trounce 680/770. This isn't based on intuition by real world gaming performance in less popular titles where 680 trails by a long shot.
Real world data shows AMD's cards perform faster in less popular games NV doesn't specifically target. Add to that latest GE titles where NV needs 780 to compete (GRID 2 and COH2) and I don't really understand why people keep saying NV's drivers are better. Scientific evidence shows otherwise. Stating NV's control panel looks better or complaining about restarting the PC after a complete driver install is one of the weakest arguments for NV's superior drivers. Most people prefer NV's drivers since they have used NV for the last 10 years and are reluctant to switch. NV already had 2 drivers that killed their GPUs. So much for their superior driver record.