[Xperia Z3 Compact Q&A, Help & Troubleshooting] clouds5:
Hi there :) I had similar concerns when I was looking for a new phone. Here's my thought process:

- When you are talking about one hand usability you can't only talk about screen size.

1. Example: While the 4.7" screen of the iphone6 is basically operable with one hand (provided you have big hands) the space that you need to be able to reach with your thumb is actually quite alot bigger, because of the homebutton placement. So when you're talking one hand use the iphone6 has actually a over 5" space that you need to be able to reach, which really is too big for "normal" sized hands.

2. Example: HTC Mini 2 (almost bought that one), the screen is 4.5" with on screen buttons meaning you only have to operate a 4.5" surface which is perfect for my hands. BUT the only way to power up the phone is with the power button on the top making it uncomfortable to use. You basically need to move your hand upwards to reach that button, while holding it with one hand and then back down again. Very risky maneuver if you ask me.

--> Z3C has none of these issues. You wake up by double tap, and control everything on the 4.6" screen. No need to reach any buttons which means you never have to adjust your hand while using the phone. That's way more comfortable and you reduce the risk of dropping it while adjusting.

Btw: Most of the time I'm using an app to switch off the phone (screen off and lock), swipe up from the on screen home button = screen off. If you don't wanna use those features: the power/lock button is placed perfectly for your thumb (right hand) or your index (left hand), whenever i grab the phone the button is right under my finger without me thinking about it.

-Now obviously in terms of actually using the phone to browse, read, game, do whatever the screen needs to be as big as possible while still being operable by one hand. But "handed" use means the furthest you will hold your phone away from your eyes is one arm length. Fully stretching your arm isn't really comfortable so let's say its a bit less than a full arm length. I personally am usually resting my arm on my belly while holding it, so thats not even half a meter (~20"). And I have to say with regular font settings the screen and more importantly the font sizes are almost too small. Coming from a 4.8" SGS3 i had to get used to the smaller fonts and screen, then I found the setting to increase font size and now it's not an issue anymore :)

-->I'm always able to rest comfortably when using it, without having to pull it in front of my face (iphone syndrom) to actually see anything... And that is the important factor for me. But I have to add: I also have a tablet. When I spend more than ~10min reading or writing stuff I usually switch to it. That was the main reason for me to get a "smaller" phone- no need for a phablet here. (4 Years ago people were laughing at my HUGE 4.3" DesireHD :rolleyes: )

-In conclusion Sony did a really good job here IMHO. Comparison: The phone has a much bigger screen than the iphone 5S, but the size of the surface you need to operate is actually about the same because of very small bezels and intelligent button placement.

But it also really depends on what you want to do with it and on your hand size. For watching the occasional movie the Z3C would be definately too small for me. If you have really big hands I guess you could easily operate a 4.8-4.9" screen if the button placement doesnt get in the way. But for me the Z3C has that sweet spot in terms of size and great hardware... When I read the specs I instantly knew that was going to be my next phone.

Another little thing: The Z3C has exactly the same weight as the iphone 6, almost the same screen size but a 2600mAh battery compared to a 1810mAh in the iphone...