Thank you very much.
Yes, it never occurred to me that D[Log[1 - y], y]
could be the same as D[Log[y - 1], y]
Sorry for not stopping to think.
I guess the reason Mathematica chooses the first anti-derivative is because of its preference for putting terms in
$y^0$ first.
If I had been dealing with y's less than 1, I would have been happy with my result...getting negative numbers inside the logarithm was a bit of a shock (not that I was actually evaluating them, but I could see that for the part of the parameter space I was dealing with it was a problem).