Most O'days in the trailerable category have a shoal "stub" keel with a centerboard. I think the 22 had a shoal keel only configuration, and the 240 is a shoal wing keel. Other than that, they are all shoal stubs with centerboards, on up to the O'day 26.
Personally, I like this combo. It gives you decent ballast below the waterline, with the centerboard that improves pointing. Yet you can still get into some skinny water. As pointed out, it also makes for easier launches and retrieves. They also sail and handle nimbly, compared to something like a ComPac 19, which has a shoal 3/4 length keel, and doesn't point worth a damn. Was sailing with a friend who races Hobie 16s, which acts like full keel boats, and they don't tack well at all. It was funny watching my friend tack my boat (based on experience with the Hobie) very slow and easy, versus the way I tack her, like a dinghy, and throw her over so she tacks in like 1/2 boat length. Fun!
I compare my 192 to the Catalina Capri 18, which has a wing keel. That keel is deeper than my 192 for a similar sized boat, and it does sit higher on the trailer than my boat.
Still, I did make an 8' extension for my trailer, so that I don't have to worry about getting the Forester's wheels way down into the water.