I'm trying to minimise my subjective involvement in the editorial, but actions speak louder than words: I'm keeping the 24L and returning the ZF25.
If I had unlimited funds and an appetite for a vast menagerie of lenses, I would keep both, because in the f8-f16 range, which I believe to more important than f2.8-f5.6, the Zeiss will give better shots if you've got time to use it.
If you subtract out Zone C, as all Nikon digital users will, you're left with a very impressive performer. What makes sense on a Nikon body, however, doesn't necessarily work as well with a full frame sensor.
Though I really would rather use a flare-free, low CA, Zeiss lens at 25mm / f11, the 24L is no slouch in the f8-f16 range, either. The convenience argument weighs heavily, then – as does the big two stop advantage. My recommendation is unreserved for Nikon users: it's so much better than the 24/2.8 AIS I had, but Canon users already have a great (if not perfect) lens at this focal length, so I agree it's hard to see the appeal.