[Xperia Z5 Compact Q&A, Help & Troubleshooting] mhaha:
Larger bezel? Do you mean the slightly more disproportionate top and bottom bezels due to the lower screen placement compared to the Z3C? Because both are literally the same in screen size with nearly identical length and width dimensions.

http://www.phonearena.com/phones/size/Sony-Xperia-Z3-Compact,Sony-Xperia-Z5-Compact/phones/8744,9611

I've been using the Z5C for 8 months, and I've never been bothered by or noticed the display being lower. And that's coming from more than a year of use of Z3C, and the Z1C before that, which were both more symmetrical.

Initially I was also disappointed with the exclusion of the magnetic port, but only a few weeks in and I haven't missed it since. Having the exposed USB port at the center bottom really helps, and I favor having a seamless edge that again doesn't eat into my skin over the convenience of a charging port that only sees use when I'm not using the phone, which as I mentioned is rendered moot by the ease of access of the USB port. I bought a DK-52 dock for charging and never had problems docking it with ease, although I had imagined it would be problematic.

As for "POS S810", I mean "piece of **** Snapdragon 810" SoC. See here: http://arstechnica.com/gadgets/2015/04/in-depth-with-the-snapdragon-810s-heat-problems/

Or you can Google around "snapdragon 810 overheat", in short this silicon is ****. Sony's done their best (arguably the best out of all manufacturers) to mitigate the impact, but in the end there's only so much you can do to workaround an inherently poor hardware design.

*EDIT BELOW*

As for the question of throttling and overheating solved by updates, there doesn't seem to be a decisive or conclusive evidence of that. With each new update, it seems there's always people reporting better battery/improved thermal alongside people saying it's worse or no change. Yes, there are mods/ROMs claiming to fix the battery and heat issues, whether or not they actually make a difference is more of a personal usage thing, you have to try them out for yourself and see if they work for you.

It may sound like I'm hating on the Z5C, but on the contrary I actually love my Z5C. It's just that after using the Z3C, high expectations have been set but the Z5C failed to deliver on some accounts, mainly the battery and thermal issues. Otherwise, I genuinely felt it was a worthy upgrade over the Z3C. I've come to accept that I won't be getting the same outstanding battery performance of the Z3C, but that's not to say that it isn't great on its own merits. Also consider that the Z3 series are pretty much dead since they're not getting official Android 7.0 support, while the Z5 series are still on the upgrade list, albeit now at the lowest priority compared to the more recent models.

So to sum it up, I don't think it's worth investing in a screen replacement that may still break after a year, not to mention potentially losing the waterproofing. The Z5C may be the next logical step after the Z3C, but has problems of its own. You need to decide if the drawbacks are worth it. At least it's been a little over a year since the phone's release, and there seems to be no (mass) reports of dying touchscreens. Yet. So it's got that going for it, which is something I suppose.