You might have a point about the fancier camera, but otherwise I would buy the smaller model. Its screen is about the same size as that of my Nexus 4, and I don't feel at all like it limits me with a too-small screen. But I do sometimes stretch to get my thumb the reach to the other corner of the screen. It is plenty big for a phone.I absolutely agree; a phone is a pocket thing. The thing is, I'm not sure that my iphone is really a phone any more. I haven't used it to "talk" to anyone in a couple of weeks.
A phone is a pocket thing. (Well, in my case it lives an ancient REI soft sunglasses case that I have on my belt.) Ubiquitous, handy, convenient, almost always with me. Small is crucial for all of that. Certainly a large screen is cool, but you need a place to put it: don't break a fundamental feature of a pocket phone by getting too big.
That is what your small tablet is for.
I have my phone with me almost always. I have my Nexus 7 tablet with me nearly as much. The bigger screen is great, yet it fits in some pockets (if I don't sit down). The Nexus 7 fits in the purse I take everywhere. When I can settle in for a moment, I don't grab my phone, I reach for my tablet.
You must have an iPad mini, right? It is a great little device, but the phablet-sized iPhone 6 Plus looks like a poor substitute, nor will it fit in your pocket. Seems a bad compromise in both directions.
But: If you are *not* someone who can put your phone in your pocket, hang it on your belt, etc., if you have to carry your phone anyway, then carrying a big phone might make sense. Frequently women don't get to wear such practical clothing as do men and have to carry their phones. In that case, a phablet-sized phone might make perfect sense. Particularly for women with big hands, and those with very long thumbs.
A final consideration: move fast and, for a time, people will oow and ah over your big iPhone 6 Plus. Kind of like bird with cumbersome plumage, it might be worth it for non-functional reasons.
And the other thing is; I don't have an iPad Mini. Maybe I should buy a Mini and the regular phone. I'll have to think about that...
The cumbersome plumage analogy also gives me pause, and I worry about the weight of vanity. I have to make up my mind by tomorrow!!