In the Cock vs. Breasts thing:
There's one reason cocks are put in the strip, and not breasts.
Hilarity factor.
I mean, come on. Cocks are completely ridiculous. They are ridiculous little things (I just know I'm going to get a "MINE ISN'T LITTLE" post). If they did not serve the useful purpose of continuing the species, no doubt evolution/God(s)/castration would have removed them, or never put them there in the first place. Why do you think the statue of David has a small wang? Because WANGS LOOK RIDICULOUS, and the epitome of male beauty should not look ridiculous.
So, therefore, a dick is funny to put on a cat in a comedic strip, though it's basically the Achewood equivalent of toilet humour. Still inexplicably funny, in a way.
Breasts, see, they ain't so ridiculous. Also, it's pretty disturbing putting them prominently in a mostly animal based strip. That is straying dangerously into furry-ism.