ED difference for D1 and D3?

Stanford is SCEA I believe. There is no gaming the Stanford system by applying early; for non athletes it's a lottery with little chance of success. The pool from which these kids are selected is incredibly deep; but as to academics and scores those accepted or waitlisted (and indeed probably a lot more) are all top shelf. It doesn't mean that Stanford doesn't screen for certain desirable applicants in EA (e.g., alum kids); it just means a normal applicant (34 ACT, 4.0 uw, most rigorous course load) has a small chance in any event.

There are many factors influencing ED rates; in true ED, there are more full payers so that may give a kid from that pile a subtle push. Moreover, each kid has a single ED application - when we are in an era where 10, 15, or even more applications has become the norm. There are lots of variables impacting the ED acceptance rate. If you don't need FA, know which school ABSOLUTELY he wants, and are right on the borderline of what the school admits, then ED is a good choice; otherwise, think carefully.

I don't know about ED at Duke or Vandy, but I know about RD.  What ultimately wasn't enough for Stanford in EA, was more then enough for Duke and Vandy in RD.  For non-athletes, it's so hard to get into these "top schools."  

The Ivies want a kid to go ED/EA because they do not have the protection of the NLI; and, there is no Likely Letter until there is a completed application.  

That means the real RD rate is even lower for non-athletes. So if you are non-athletes applying for an extremely selective D1 college (e.g. Stanford, Vanderbilt, Duke, etc.), you'd better apply ED. Make sense?

For certain kids at certain schools, yes, it makes sense.  For example, if a kid  really wants to go to Lehigh, which is one of those schools that states that demonstrated interest is a factor in admissions, then there's no better way to demonstrate interest.

But I don't think it's possible to make such a generalized statement, partially because the schools do not (as far as I know) break down the academic numbers for applicants who apply ED vs.  RD.  Duke, for example, has an ED admit rate more than twice the RD rate.  Legacies and full-payers and maybe athletes will account for some of that difference, but as for the rest, I suspect it's two factors:  First is the applicants themselves self-selecting.   A 3.5 student who has dreamed of attending Duke might waste $75 of his parents' money applying RD to a school he knows he has no chance getting into, despite all the glossy brochures they've been sending him. But he's less likely to waste his single ED application on a pipe dream than to use it on a school like Lehigh where it might really help. So I think if you saw the average GPA and SAT of the ED applicant pool, it would be substantially higher than the RD pool.

Second is the school's admission process.  They have a certain model in mind of what a freshman class should look like.  If you really want to go to Duke, and you're a middle of the pack applicant in terms of test scores, GPA, and EC's at that school, and you're not some kind of extreme overachiever or prodigy who will get in no matter what,  then you might  be better off applying ED because they are going to take some guys like you to compose the class and they are going to reject some guys like you, so it's like giving yourself an extra pitch in an at-bat if you apply ED.