Larger is better, right? Well... not if it bends. A large amount of iPhone 6 Plus owners have complained that the product curves in their pockets. However, the slightly smaller iPhone 6 has no such problem. See my point?
I've heard of broken displays and cracked mobile cases, but I've never heard about a phone that you can bend in your pocket, so when I first read about the curving of the new iPhone 6 Plus models, I though it was some kind of hoax. Sadly for Apple, it's not. If your pants are tight enough or you apply enough force (not that much actually), your iPhone 6 Plus will get distorted.
What's funny is that the regular (cheaper) iPhone 6 devices don't have this issue and seem to be much more durable. I'm no engineer, but I guess that the difference in sizes of the two models is very important structure-wise. The aluminum material used in both phones has to cover a larger surface on the iPhone 6 Plus, which would probably mean that the surface will become less resistant unless you make it proportionally thicker.
In case you were wondering, other phone models, such as the HTC One, Motorola Moto X and Lumia were put to the same test as well. The HTC One had its display pop out a little, but it didn't curve, the Moto X simply didn't budge or make any noise, and Lumia, which is a former Nokia brand ... Well, you know what to expect in terms of durability there.
Here is a video made by Lewis Hilsenteger who demonstrates how easy it is to bend the iPhone 6 Plus.
Small piece of advice: if your phone somehow curved, don't try to apply force from the opposite direction to unbend it.