All right, I've now had two more skates, 1 more fully on ellipse, where I was paying attention to things like acceleration and agility (we're talking relative terms here...while not a member of the Loyal Order of Water Buffalo, my lightweight days are behind me), and one where I started with ellipse and did a blade change back to Quad 1. And the winner is the Quad 1. More jump, more pop, more explosive starts, sharper turns, better pivots, better feeling of front of skate. It's funny, I didn't really notice anything bad on the ellipse, but the minute I put the Quad back on, the guys I was with were all wondering what happened...
So, I'm going to agree with @pgeorgan, there's something less aggressive at the front that is slowing the ellipse down.
PS - I know I'm dating myself with the LOWB reference...ah, childhood memories of that and classic animated flashing sky Spiderman.