Genma is the best defined, and in fanon circles, the most reviled of
the two parents... whereas Nodoka is portrayed as somewhat innocent
yet strictly traditional in many senses.
What we know of Genma varies from Manga to Anime, but there are some
consistencies.
Genma has traded Ranma for a variety of different things. Genma has
an obsession with perfecting Ranma's art, as demonstrated by all the
subsequent events that make Ranma who he is. The Cat's Tongue, the
journey to China, Jusenkyou, etc.
Genma is often presented as a coward in fiction, but where does this
cowardice stem from? Many of the actions he takes are to protect Ranma
in some sense, unless I am missing something.
Nodoka, on the other hand, is insinuated to be ready and willing to
kill Ranma and Genma throughout the entirety of the manga since she is
introduced as a character, were she to find out that Ranma's curse
turned him into a girl. However, in the last few manga issues, it is
shown that Nodoka determines manliness by male perverseness in one
sense. Spying on girls in states of undress and such.
While it may be easy to determine that Genma is the worse of the two,
since Genma has had the most influence on Ranma's particular psyche...
would it have been better for Ranma to have stayed with his mother,
and what sort of person would he have turned out as?