Technically, the stocky builds are "robust" and the willowy ones are
"gracile".  There are regionalisms abounding, but those two words are
known all over for animals in general.
 
Some considerations if looking for a robust build: If there are also
shortened limbs but normal size trunks it is possible that a form of
dwarfism may be at play.  Some of these carry no complications, but others
can have cartilage difficulties and other medical considerations that can
be difficult to treat and painful for the individual.  We had a little
girl in that position years back, and she required a great deal of special
care to be comfortable.
 
Short faces are not a problem if the mouth is still large enough for the
teeth, but not all short faced individuals so have large enough mouths.
When just barely large enough the teething can be harder and resulting
gnawing (including of fingers) to try to ease painful teething can be
worse.  When not large enough there can be need for dental surgery when
teeth erupt in ways that they should not.
 
Generally, in mammals robust builds are associated with greater strength
and more stable joints while the gracile builds are associated with more
athletic flexibility, but within a species the degree of difference is
likely too low to notice usually in everyday actions.  (Extremes in humans
include ballet dancers vs.  olympic lifters...)
 
  ---
 
When lethargy and abdominal ascites exist together the three most common
causes that the vet will check first are based in the heart, liver, and
kidneys.  X-rays will help see if there may be dilative cardiomyopathy
(but not necessarily hypertrophic cardiomyopathy), and may well have to
be followed with ultrasound to know many essential points that will
affect the treatment.  A CBC is normally done, as well as kidney values
and liver values (keeping in mind that many liver values are not
diagnostic in ferrets, though bilirubin is one to watch).
[Posted in FML issue 3649]