Like I said, I last saw Momo (naked) in March. So direct comps are a little fuzzy. Best guess is Momo is literally a bit larger in terms of absolute volume, but she's both a bit taller and larger-framed, so in terms of relative size, I'd say Yume is pretty close. And given the better framing, plus perfect density and drop, I give the edge to Yume in overall quality.
I see you once reviewed Apple at 38 Mate. By coincidence, with Yume now getting the #10 slot in the compendium, that pushes Apple to #11 all time. (Apple is one where her boobs in absolute terms are probably bigger than Momo's - might be like 3rd or 4th from my list in total volume, but because Apple is so tall the relative size wasn't as impressive. I mean, still impressive, of course.) I now have Momo at #13. So of course these are razor thing margins and it's absurd to rank to this level of false precision. But why should that stop me?
Point is: Yume has a tremendous rack either way.