I liked both and for a long time I liked De Niro better.
However, as I've gotten older, I now favour Pacino more.
Reason is, I think, is despite how bad the film is, I always find Pacino more interesting to watch. He has better screen presence than De Niro IMO.
That's why I would rent a film starring Pacino despite hearing how bad it is (eg 88 Minutes). I wouldn't do that for De Niro.