The Xiaomi Mi 11 Ultra has been soundly thrashed by the Sony Xperia 1 III in a series of speed tests. While both phones sport the Snapdragon 888 SoC and have 12 GB RAM each, it seems the new Xperia 1 III enjoys enhanced Android and RAM management optimizations over the Mi 11 Ultra with its heavy MIUI 12.5 overlay.
https://www.notebookcheck.net/Xiaomi-Mi-11-Ultra-left-for-dead-by-better-optimized-Sony-Xperia-1-III-in-grueling-battery-of-speed-tests.550723.0.html