Screen size, resolution and quality are some of the most important features to consider when choosing a smartphone.
Xiaomi Redmi K30 Ultra's 24 AMOLED and Xiaomi Mi 10 Ultra's AMOLED screen have exactly the same LCD size of 6.67" so we don't have a winner here.
Besides comparing the LCD sizes, another specs that we find useful to compare is the ratio of screen area to total surface area of the phone (screen area/total surface area).
Xiaomi Mi 10 Ultra LCD covers 90% of its surface which is only slightly higher then Xiaomi Redmi K30 Ultra's 87%.
Screen size is only one side of the story, resolution is as important in most cases.
Xiaomi Redmi K30 Ultra's 395ppi pixel density is only slightly higher (9ppi ) than the Xiaomi Mi 10 Ultra's 386ppi pixel density.