The original Battlefield 3 PC article focused on building either an AMD or Intel system using AMD Radeon HD 6000-series GPUs, mostly because the cost of an equivalent NVIDIA GPU exceeded the budgets for those builds. This time the systems are specifically built around NVIDIA 500-series GPUs using the same budget points, plus one special build that most of us can only dream about.
NVIDIA FTW! Don't know why but I've always preferred NVIDIA. They're drivers are much better imo.