Too me it has always depended upon budget. I had a friend recently come to me looking for an update to his old HP system he bought. It was having hardware issues and just was too slow for gaming. He had Nvidia 550TI that I helped him get back in the day when he bought that horrible off the shelf system. Because it was the best bang for the buck for the money he had.
Well he's not made of money so he asked me what I could do for $250. He needed a power supply, motherboard, memory, cooling, CPU, HDD, and new vid card. He was going to pass what he has to his son so the kid could play some games somewhat too. $350 isn't that big of a budget for all that but I managed. I had an older Antec Neo 520W I had picked up on a deal for $30 back in the day. As well as a 1TB drive for $40. I tossed those at him for what I paid since I wasn't using them. They were going to be for a build I never got around to.
That left me with $280 for everything else. I picked up a AMD 740 with a decent full size atx size board. Is it the best? Hell no. Is it the best I could do for the money? Hell yes. Paired that up with 8 GB of some ok DDR3 and an AMD 7850 and I was able to stay at his budget with deals I found.
It won't be a beast of a gaming system, but it doesn't need to be for mostly playing WoW. If he had a $600+ budget I would have picked something else for sure. More than likely gone the intel route. The price was what left me looking at the overall best performance for the money I could find. In the budget range I was in, I was stuck with getting what I got.