The 180/4 has a minimum focusing distance (object-front lens) of 1,3m, the 250/5,6 of 2,2m according to the datasheets.

http://lenses.zeiss.com/camera-lense...rt4180cfe.html

http://lenses.zeiss.com/camera-lense...t56250cfi.html

The 180mm is also said to be well suited for macro work.