I was pretty set on the Plus, but here's my point of view, based on originally grabbing the 6 Plus, then switching to the normal 6 and then 6S.
- The larger screen is sharper, and I really like that
- The larger screen isn't put to good use at all. I found that most of the time, websites displayed the same (not showing more content), just slightly larger, and this generally applies to most apps too. In an ideal world, the Plus would have better layouts for apps utilizing the extra space, but it's not like that.
- The 6+ had to do a lot more work to render its screen than the 6 (because of the resolution being calculated at 3x and downscaled or whatever), which made it feel noticeably more sluggish. I found a rather large difference with that generation. They might be the same now I guess.
- The battery in the older generations was pretty far apart, but according to what we're hearing, they're only an hour apart now. That's a plus point for the smaller phone.
- The Plus cameras had OIS, which to me, is a huge benefit. Now both do, so the point is moot.
- I never, ever got used to the size of the Plus in terms of handling. Screen size of course, you get used to that. But I have massive hands, and never liked the way the phone handled, or felt in the pocket. Felt like I had to spread my hand pretty wide to hold it. Many activities had to be 2-handed. This is the biggest issue with the Plus to me.
- My thoughts initially with the Plus were that I wouldn't need to use an iPad as often, but I found a lot of difference in practical use. The way websites render and show, and the way you interact with them is a different enough experience that I found I'd prefer using an iPad wherever possible. Since that was the case, I thought why not downsize and be more comfortable, and I was.
- Moving to the 6, it felt faster and far more pocketable and usable, and the 6S was of course, the same. Didn't feel any regret, need to change, or go back.
So with the 7/Plus, I was thinking it would have a far superior camera, far superior battery life and of course, that sharper screen, and it seemed like the right choice. Looking at it now, after the reveal, the battery gap has closed, and the camera isn't really much better IMO. Not sure if both cameras have OIS on the Plus, and even if they do, the 56mm-equivalent lens is f/2.8 - a bit of a downer for me. Now, in daily usage, I would use the 56mm lens about 80% of the time (I am a photographer, so I already know 56mm works better for most applications apart from landscapes), but that size is just too much to pocket IMO. Probably going with the 7.