Is this even a surprise really? Not only the Xperia has a stock AOSP UI, but it also has a great memory and battery optimization. I had multiple experiences using Xiaomi phones with MIUI and let's just say that I definitely DON'T miss them when I flashed custom ROM.

Its something not-indepth-reviewer who only use the phone for few days for review will notice. But UI quality is something that actual longtime user will notice.

I use Redmi Note 5 ai (SD636+6gb ram) and in that Miui is pretty much do the work, not much problem other than sometimes the notification sound didn't come back on after i put it out from silent mode.

And then i switch to Poco X3 (SD732+8gb ram) which have Poco overlay on Miui overlay, it kinda sucks.
Bugs while not that often, is more present than in Redmi. just yesterday i have 2 battery symbol bug. And the camera app despite 64MP QUAD CAM~! specs, the camera app (&@!(& lags so badly. there is distinct more than a second lag between pressing and image taken. Its something that my previous redmi works flawlessly.

Not to mention the slightly less performing SD720 in RealMe actually game more smoothly than SD732 in Poco because the Poco overlay on Miui overlay is so damn inefficient. Also yeah, 8gb ram but browser page reload everytime you minimize it, whats the point.

While its still pretty decent value, the sacrifice is still there ever present on your daily use. So i can see the near stock Xperia have its edge on day to day use.
i'm currently planning to buy old flagship LG V50 which sold is in the same price with Poco X3 to compare

Samsung S21 Ultra: dead
iPhone 12 pro max: dead
Xiaomi 11 ultra: dead

Reviewers: something something Xperia 1iii is overpriced and competitors provide better value.

Does anyone even test these things in real life?