iPhone 6
- No compromises with one-handed use - no extra effort to position hand
Everyone has different sized hands, but I think my fingers are pretty long, and I'd disagree with this point. I think that the 6 is still a bit unwieldy. And going from the 4S to the 5, I thought that was a bit more unwieldy as well. Reaching the top left corner of the screen of a 5 required a minor adjustment. Reaching it on the 6 is very uncomfortable, and typically requires using the reachability function.
So, IMO, if one-handed use is important to you, I think you need to be aware that moving up to the regular 6 will be a step back in the comfort level of using it one-handed, but it can be done. Similarly, going up to the 6+ will add yet another degree of uncomfortability, but with that phone you *also* (unless you have very small hands) can probably find ways to contort/shift your hand to use it one-handed.
Personally, I want to have my cake and eat it, too. I want a big-screened phone that I can use one-handed. Is that something that is impossible to pull off? I don't think so, but it will require a new physical design and changes to the UI. The UI changes (e.g., guidelines stating that it's a no-no to put any on-screen buttons at the top of the screen) could be implemented by Apple and benefit existing iPhone 6+ owners. But the hardware changes would need to be implemented in a future product, though some of them could be accomplished via add-on products.
For example, I could see smartphone companies designing their phones with a bottom-heavy wedge design, making the top of the device ultra-thin and light, with the battery being concentrated in the bottom half. I believe this would make the phone less drop-prone. Also, the sides and back of the bottom portion would be coated in a grippy material, rather than smooth metal or glass.