We're fans of both the Rainsong and CA guitars and customers ordering them from afar often ask us how they compare, so we recently made these videos.
If we had to sum it up briefly, we'd say that the Rainsongs offer a truer acoustic guitar tone and are superb for fingerstyle - a very balanced instrument for serious players.
The CA's are a lot more bassy - and fun to play (the CA's tend to swing both ways between acoustic and electric, like a crossover: overdrive a Cargo through a tube amp to make it sound like a Tele). Since Peavey bought the company a few years back, they've made some great improvements to them, like intonating the bridge and re-setting the neck angle.
Here's a couple of quick demo's recorded with a Zoom camera about 6 feet away:
Rainsong 12 Fret Parlor vs CA Cargo:
http://youtu.be/vVOCY_7dAt8
Rainsong Shorty SG vs CA Ox Raw:
http://youtu.be/pOJzZAzxD0Y