If there's nothing in the comparison in https://www.gsmarena.com/compare.php3?idPhone1=9738&idPhone2=9646 that makes one of them clearly better for you than the other, both will be good amd none of the two will be bad.

You can either throw a dice (1,2,3 = Xiaomi, 4,5,6 = Galaxy) or buy the cheapest of the two (why pay more than needed?).