This particular forum prioritises price/performance very strongly, even if the differences are relatively minor. My feeling is that general hardware looks at the overall package. They have a more honest assessment of driver quality and extra features and tend to associate value to Nvidia cards for those reasons.
Having owned recent AMD cards (7970's) I don't think AMD has its act together, the amount of poor performing games on release, the severe bugs and everything else just left me with that feeling that the drivers are still rubbish. Not as bad as they once were (early AMD cards I had didn't even install) but compared to Nvidia they are much worse. I experienced this difference myself having previously value only price/performance alone.
On price/performance I can't disagree with the 290 its the better buy on that aspect. But the question really is which card would I buy knowing what I do now and I would buy the Nvidia card even if its more expensive, the price difference would have to be pretty large for that not to be the case, because AMD's 7970's drove me to the point of madness. Because for that extra price I get something that works on release day, which is massively important to me and its cheaper to buy Nvidia first rather than a 290 and then a 780 after it. AMD needs to get their drivers sorted, they need to start fixing the bugs their customers raise and they need to take the software seriously, until they do that its hard to recommend them unless the difference is enormous and its just not big enough a difference for me to say get an AMD card. Its not brand loyalty, I am just still pissed with AMD and the way they treated the problems I had and how they still treat the bugs. Leaving the 7970 users to rot on frame pacing will have lost them a lot of customers in the future and I will need good proof in the future that they have fixed their problems before I even consider them again.
