Yes, the size difference is much. Plus on the Zeiss lens you do not really
need a hood because of the superb coating.
Which is better will depend what you want to do: you want corner
to corner sharpness at f1.5, only the CV can do this. The Sonnar is
the better portrait lens, IMO, but a bit more complicated to handle.
F4 or so and up it will be hard to detect a difference at normal enlargement.
BTW, both lenses go down to .9m min distance. You can do very good
portraits (similar DOF) with 50/2 lenses that go down to 0.7m, and fill
the frame more. There are several great 50/2 lenses out there.
Best,
Roland.