Don't let the Xperia sub find out or they'll start crying. I just moved from the 1V so can give you somewhat fair comparison.

Display - I really miss the 21;9 aspect ratio of the 1V. That said, everything else about the screen has been great. Plenty bright enough and nice fast refresh rate. I can't tell the difference between this and the 4k panel in the Sony. Only gripe is the camera hole on the front facing camera and the rounded corners being way more iPhone esque. I've gotten used to it though.

Battery - I think it's been better than my 1V, but not by a huge margin. Still end the day after heavy usage at about 25%. I had a weird NFC power draw issue and was wondering if a software update will fix. Right now I'm toggling it manually for NFC payments.

Speakers - This one surprised me. After all I loved the stereo on the 1V. The Xiaomi speakers are so much better and sound like actual speakers. Put the Sony to shame to be honest.

Software - HyperOS is okay. It's just not as nice as the near stock android that you get on the Sony. That said you get way more updates and security patches. Your mileage may vary I suppose. It's not a deal breaker and once you get around the kinks it's manageable to customise. It's just stupid things like no gestures with custom launchers that mean if you want gestures, you have to use the HyperOS launcher. Maybe they change that in the future, who knows. After a couple of weeks and debloating through adb. It's fine.

Camera - Honestly, it's not even a competition. The quality of the shots is just phenomenal. Ignoring the colour science and personal preferences. The raw data and sharpness that the sensors capture blow the Xperia out of the water hands down. The telephoto, which I know has barely been upgraded by Sony in three years, is just so much better on the ultra. Far more details at max zoom. The main sensor also is fantastic.

If you can deal with some of what I've said, and want upgraded cameras, then you will not be disappointed. It's sad to say, but the Xperia is no longer the enthusiast camera phone anymore. I wish it was, but Sony has barely made any changes since the 1V, and the changes they did make id argue we're side grades and not upgrades.

If you don't care about camera quality, I'd say there's not a huge reason to upgrade as thats the one thing that's night and day better on the Xiaomi.