The student whose percentages are mostly in the lower end of the grade ranges prefers just the grade, while the student whose percentages are mostly in the high end of the grade ranges prefers the percentages.
For example, if the grading scale has 90-100 = A, 80-89 = B, 70-79 = C, etc., then the student with mostly 99 and 89 grades will prefer to have percentages listed, while the student with mostly 90 grades will prefer to have only grades listed.
A similar situation exists to a lesser extent with the SAT and ACT, where the concordance tables tend to have four SAT scores matching one ACT score. At the very top end, it is easier to get a “perfect” 36 on the ACT than a “perfect” 1600 on the SAT for both this reason and the fact that the ACT composite is a rounded average of the subsections instead of the sum (36/36/35/35 gives 36 composite on the ACT, but you need 800/800 to get 1600 on the SAT). This can matter for such things as the Presidential Elite scholarship at Alabama (3.5 HS GPA and either 36 ACT or 1600 SAT).