A good single action revolver can be quite serviceable as a home defense gun. As long as you select a premium hollow point load that you can shoot accurately and reliably, then it will do as well as any, provided that the user is familiar with the operation of such weapons.
The disadvantages to a single action revolver are that it must be manually cocked before each round can be fired, not making it the ideal gun for follow-up shots, except for those intimately familiar with such operations. Also, most of the older single action revolvers have the firing pin resting on the cartridge itself, making a round in the chamber susceptible to unintentional discharges if, say, the firearm were dropped on the right spot.
The cowboy-action shooting games are always a lot of fun, and if you don't have all of the needed gear, a lot of times, someone will be willing to let you borrow some. It's a very friendly group of shooters, and their marksmanship skills are as good as any IPSC / IDPA / USPSA shooting league.