I would agree that they are in the same league of selectivity, though NEU so probably closer to 30% with new data. I am curious why you consider transfer acceptance rates more important though as I’ve never heard that before.
Both have high/comparable freshman retention rates, but NEU enrolls double the transfer students by volume. I think that would account for the transfer difference. That is curious as by my calculations of retention rates, NEU graduating class sizes grow over the years while BU’s will shrink.
In terms of freshman, both NYU and BU are about 5% higher using NEU’s expected current numbers. I would not call that significantly more selective in the connotation of the word used above. Perhaps scientifically significant, as to make a small distinction. Overall, BU / NYU / and NEU are going to be in the same range of selectivity for a good bit.