Keep this in mind, if the Cajun accordion only plays in C, it actually plays in C and in G. G is much more fiddle friendly. Actually for Cajun music this is what they do. Kind of like cross-harping on a harmonica. Take a C accordion and play it in G; this is done often in Cajun music.

Also, the sound of cajun accordion is often different than Zydeco accordion. Zydeco music often uses accordions with unisons that are slightly detuned from one another, while Cajun uses octave unisons. I don't quite know how to explain it in words. Hopefully that makes sense.