Just my opinion....
Technically speaking there should not be a difference. According to most posters as well as knowledgeable people I spoke to, the difference is in the Labor and PD getting current.
However, based on the postings I ve noticed and the time it takes to go through from the ND to the FP through to the AD, I believe there is some discrepancy which points to some favorable treatment for EB1 and EB2 applications. It just seems to go through faster. Let me warn you here that this is just a gut feel. I have no stats to back me up on that. It would be an interesting exercise for sure.
Hope that helps.
Regards
seebeekay