Yeah, I don't think there's much debate that the 2004 DA teams are better than ECNL.I think you are overlooking the fact that many of the ‘03’s and above were ECNL players prior to this season. So maybe they were already top US Soccer prospects going into this new cycle and these players simply decided the best situation for them was to remain on their current teams.
That said, there are plenty of 2004's who opted out and will play ECNL or even SCDSL so they can play other sports too.
for starters (and including links to other studies on injury): http://www.stack.com/a/new-study-re...ort-athletes-have-a-better-chance-for-successResearch based? Point me to the research, please.