It's a good question and one that isn't limited to Apple smartphones. For the last few years, the chasm between a large smartphone and a phablet has shortened, but the truth is, in practice, there is still a substantial difference between a 4.7-inch (or even 5-inch) phone and one that is 5.5 inches.
For us, the answer of "Which iPhone should I buy?" all comes down to how you use your device. Specifically:
How big are your hands?
Although we don't think hand size is necessarily indicative of whether a user should choose the iPhone 6 or the iPhone 6 Plus, the size of your hands still plays a role in what phone you may find more comfortable.
That's because even with Reachability, the iPhone's new screen-shifting feature to make using the iPhone 6 Plus less of a chore, the iPhone 6 Plus is just a beast of a device.
It's more than 6 inches tall and 3.5 inches wide. To put that in perspective, you can fit an entire original iPhone onto the screen of the iPhone 6 Plus and still have room to spare. It's huge. Its battery alone is almost as big as the iPhone 5S.
If you have small hands like I do (seriously, my hands and wrists are ridiculously tiny), even using the iPhone 6 Plus with two hands might feel off. And one-handed? Forget about it.
That said, if you have larger hands, the iPhone 6 Plus, even with one hand, might not be that bad.
Now, there are always exceptions — some people with small hands love a big phone and some large-pawed individuals prefer something smaller — but if you're an extra-small glove size, the iPhone 6 Plus is probably too big.
We put together this chart to show thumb reach for the average person based on height. This chart is just an approximation because some individuals (i.e., moi), have a thumb reach that is far more constrained than their height would suggest).
Do you like to use a phone with one hand or two?
Somewhat related to the hand size question is how you actually use your phone.
Do you frequently use your current iPhone with one hand or are you almost always double-fisting it for texts, emails and scrolling through web pages?
If you like to use your phone with one hand — say, on the subway or for a quick glance — the iPhone 6 Plus is probably going to be too big for your needs.
On the other hand, if you almost always have your phone in two-handed mode — or you like to hold it in landscape, the iPhone 6 Plus might be perfect. Heck, you get even more room for typing out texts and viewing videos.
One of the reasons bigger phones have become increasingly popular is that if you use a phone with two hands, you are less likely to notice the sheer size of the device.
Do you also own/use a tablet?
For us, the single biggest distinguishing factor between the iPhone 6 and the iPhone 6 Plus comes down to how you use your phone.
If your iPhone is your primary device — you don't have an iPad Air or iPad mini and don't lug your laptop around everywhere — the iPhone 6 Plus immediately becomes more appealing.
That's because its bigger size really does lend it to being in a sweet-spot between a phone and a tablet.
There's a lot to say about individuals who don't want to carry around more than one device and like to just have the iPhone as their primary personal computer. For those users, the iPhone 6 Plus might be perfect.
On the other hand, if you have an iPad or other tablet, the need for a larger-screen iPhone 6 Plus might not be as great if you have an iPad or other tablet, the need for a larger-screen iPhone 6 Plus might not be as great. The iPhone 6 has a larger screen too, and coupled with a separate tablet or laptop, that's probably enough.
For us, it all comes down to how you view and use your device. I personally almost always travel with my iPhone and my iPad Air. As result, I'm happy to use my iPad Air when the need arises to type longer documents or to spend more time watching videos.
My husband, on the other hand, really only likes to have one device with him. In fact, he frequently carries his iPad mini around in his pocket and uses it almost as a phone. The iPhone 6 Plus would probably replace his iPhone and his iPad mini.
The final consideration between and iPhone 6 and an iPhone 6 Plus is the size of your pockets and/or purse.
That's because the actual act of carrying around a larger phone can be more complex than you might think. The iPhone 6 will barely fit in some of my smaller handbags. The iPhone 6 Plus? Forget about it.
My iPhone 5S doesn't fit in my front pockets and still peeks out a bit of my back jeans pockets. The iPhone 6 won't be decidedly worse, but it'll be more snug. I would have to take a time machine back to 1998 and put on some cargo pants to get pockets big enough for an iPhone 6 Plus.
And yet plenty of jacket pockets will hold an iPhone 6 Plus quite comfortably. Likewise, the iPhone 6 Plus will fit just fine in medium hand bags and larger.
So think about what you wear, how you carry your gear and if you're a guy, if you're willing to start carrying a man's bag.
What iPhone 6 are you buying?
Let us know in the comments.