Just a reminder that the subject is BOYS ECNL, and not girls. It is very, very different. The ECNL on the girls side became similar to boys DA because there was no girls DA then. Perhaps your experience in the girls side is not allowing you to recognize just how different boys side is.
I have boys playing and one of them played DA in the last two years of age groups. Its not a debate on the boys side. Its just a fact and it is what it is.
As for playing a championship between the two, I would argue that there are strong teams in SCDSL, CSL and ECNL. That's not the point.
The point is its USSF that runs DA and its USSF that picks the national team, not ECNL or US Club Soccer (who is sanction by USSF, like USY Soccer is). For the boys youth national team selection, vast majority come from DA teams and not from ECNL or other (not to say that there isn't handful from here and there). The whole purpose of DA is to find youth players for the national team pool.