I think for the extremely competitive school, they’re all equally hard to get into. You may find yourself to be rejected by Cornell ED but accepted into Harvard RD as each school is looking for different things. You might be an attractive applicant for one school but no so much at the other.
Based purely on statistics, Cornell ED has the highest acceptance rate at roughly about 27%, the number is a little skewed as a lot of athletes, and legacy (who have an extremely high chance of getting in based on their hooks) apply during the early round, but it technically is the ‘easiest’ to get into out of the schools you picked.