We made the mistake of not using EA in DD's round and the wait was very very painful.
Typically, ED is for someone who like the school a lot, could afford it w/o FA, and whose stat are just boarderline. ED give you some edge in admission but you can not compare FA. You get in, you need to go (most of the time)
My understanding is that SCEA does not really give that big an edge like ED.
EA only let you know the results early.