With the swing keel you can raise keel up to make it easy to get on to a trailer or to get close to shore. It is usually lighter than a fixed keel and has extra maintenance points at the pivot and at the winching device. Swing keels may require some type of housing in the interior of the boat that will take up some space. The slot that the keel fits into also has to be kept clear of gunk and growth. Usually the rudder will also have a type of pivot arrangement so it can be at the same depth as the keel.
The fixed keel usually will have more mass than the swing keel and might have a better foil shape. A fixed keel boat should be a bit more stable than a swing keel, and have fewer maintenance issues. But with the fixed draft depth, which is usually deeper than that of a raised swing keel, you have more of an issue when trailering and can’t get as close to the shore when you want to mess about on dry land.
I think the O’day fixed keel on the 22, sort of shallow draft long chord keel is meant to get the best compromise of low maintenance and easier trailering. Typically, a deeper draft with shorter chord would sail better, but you would would then have the issues of trailering, etc.
