There's always wild speculation on these forums about the number of defects in the devices sold. People give numbers to the amount of defects all the time, and though they're all just rampant speculation, they treat their numbers as facts. Most of the posts on forums are complaints, because people are looking for solutions to problems that they either have, or perceive that they have. While it's true that there are more complaint posts on forums, it's not valid when people base numbers on the theory that anyone not posting on a forum is not having problems. I'm sure that there are people who, when sold an item with a defect, don't waste their time posting here or anywhere else. They just go back to the Apple store or Best Buy or whereever, and get their phone exchanged or serviced. Lots of people spend time on forums, know about them, and use them, but when I mention macrumors to many of my friends, they have no idea what I'm talking about. That includes Apple and Android users. This forum has a LOT of members, but is in no way representative of what the general population knows or doesn't know.
The only people who truly know the number of defects is Apple, because they're the ones that get all of the returns and exchanges. And you'll never get those number out of Apple.
If you're interested in the iPhone 6 or 6 Plus, give it a try. You have nothing to lose, because if it's not for you, you can just return it and pick right back up with your current phone. If you get one and it's defective, just bring it back.