While the profiles of students admitted ED and RD are, on average, quite similar (which leads to the Admissions Office saying that the admission standards are the same for ED and RD), the statistical odds of being admitted ED are much better. One-third of ED applicants are admitted whereas the overall admit rate (ED & RD combined) is just 17 percent. Keep in mind, however, that the fact that the average student profile for ED is about the same as RD may be somewhat misleading due to the fact that recruited athletes (lacrosse players for instance) are usually in the ED pool and their GPA and SAT numbers are frequently lower than average, which suggests that the numbers for other ED applicants may be, on average, somewhat higher. Nevertheless, the fact that Hopkins is your first choice, as evidenced by the ED application, is a positive factor because students who are attending their first choice school tend to be happier. This is a big reason for having ED in the first place.
If anything, the odds are that you would get a better FA award if admitted ED than if you were admitted RD. Again, the standards are identical, but there is a finite pool of money available for FA. Hopkins strives to meet the anticipated need for all admitted students but this is not a guarantee (and keep in mind that your parents' view of what is needed is likely to be higher than most college financial aid offices' view). Early admitted students are likely to get their full anticipated need under the formula awarded, whereas that is true for RD admittees only as long as the available funds hold out. If the money gets tight, the awards necessarily must go down. And since freshmen admissions for US applicants is need blind, the University can only guess about how much money is needed to meet all admitees full need.
The issue with ED for people who need financial aid in order to attend is not that the ED award may not be as generous but, rather, that you are not in a postion to compare awards from other schools since you can only apply ED to one place. Schools formulae for determining EFC differ, and schools also differ on the way they look at certain assets. So it is entirely possible for two schools with identical tuition and fees to both award what they feel is a students full anticipated need yet end up with entirely different numbers. Thus, the risk you take with ED is that you might have gotten a more generous award elsewhere, but you will never know. So if you really need a lot of aid (EFC is very low), you may be better off applying RD.