In most cases, the ED2 deadline is the same as the RD deadline, although the notification date is obviously much earlier. But since admissions is getting all of the applications at the same time, are the ED2 applicants compared with the RD applicants?
To answer this questions properly you would need to contact or know someone who works in the admissions department at every school that offered ED2 and RD. But it would be logical to think that, in general, the ED2 students are reviewed first since the notification date is earlier and they have committed to attend if accepted.