Depends what you mean by stable
Bill,Having the ballast lower, like with the swingkeel, theoretically allows you to carry more sail in heavy weather. In reality, this just isn't so. All these small, light boats have a lot of weather helm in strong winds. In fact, some have been known to spin completely around in a gust. With a boat that has only two narrow fins (centerboard/swingkeel and rudder) for lateral resistance, you will become unstable as soon as one or the other is overpowered by the sails and stalls (is pushed sideways through the water).The O'Day 25, with its stubby fixed keel and centerboard, is not as efficient going to wind in light air but is less likely to throw you in a blow.Either arrangement can be self righting. Either can be knocked down by a gust. Either can be rolled by a wave from abeam.There are so many other factors to consider when buying a boat. Don't give the centerboard vs swingkeel issue more importance than it deserves. Every boat is a compromise. Select the one that best suits the way you want to sail.(see link below)Happy sails _/),MArk