Somewhere, either on the Dimarzio site or some other related site there's a comparison. The Original IBZUSA doesn't match directly to anything, whereas some others are pretty close, and the F3 -IS- the Super 3 from what I understand.
But 15k is not like a PAF, those range from the high 7's to the mid 8's. I sure wish I could remember what the comparison was, but I will say that the original IBZUSA is the least like another Dimarzio. I remember reading it saying "It's not really like that pickup." Whereas the other comparisons I could understand.