Can't be proven either way I guess but if AMD admit there are ongoing issues
http://www.techpowerup.com/178129/AMD-to-Fix-GCN-Latency-Issues-with-Driver-Updates.html?cp=2
http://www.anandtech.com/show/6857/amd-stuttering-issues-driver-roadmap-fraps
(in which AMD software guys sat down with Anandtech guys to discuss the issues)
then that has an impact on brand reliability, which will eventually have an impact on market value.
Look what happened to Apple after it ditched Google Maps. Bad PR reduced share price. AMD's driver reliability in certain set ups is an issue. If you looked back you might see Fermi's toaster jokes and power draw problems hit Nvidia's market value. Ultimately profits are driven by many things but solid performance will always help and little hiccups here and there do not.
Generally speaking it is not as simple as that .There are some other things like partner support / bribed press/ social media marketers etc . May i point you to zealot nvidia defenders while AMD/ATI had better products or how people close their eyes to nvidia driver problems .
May i point how tech press closed eyes to nvidia 8800GTS 320 MB problems or intel socket problem http://www.anandtech.com/show/2859 AMD would get tortured and executed for something like that or how most went silent with intel errata problem at beginning of core2duo era.
Do you know intel i820 chipset problem ; it was designed for rambus originally but intel used with sdram and users had memory corruption problems , motherboards called back in lucky countries .But you can see AMD problems all over net
AMD can have the fastest, smoother card etc. Xfire fixed and software fully optimized with the best Game bundles with a 4 month lead and it still won`t sell more chips than Nvidia. AMD do not have a loyal customer/fan base as Nvidia (Just look at sales of 77/78 vs 650/660). AMD had a massive lead in lower/mid end for 6 months and still didn't sell as well as when nvidia released; meaning people waited 6 months for nvidia lower/mid cards that were slower, more expensive and used more power with no games over something AMD had from day one (Thats insane loyalty).
The AMD customers/fans will switch to nvidia with a drop off a hat if Nvidia is better, whereas Nvidia customers/fans will not even if nvidia is worse (Performance/price doesn't matter to them).
AMD`s biggest enemy is AMD itself = Marketing and people in charge of GPU Reviews