I like the DAO revolver because it is simple point and pull, but has proven very safe in LEO hands(minimal avg training) and very fast(Jerry Miculek)
The difference between Mr. Miculek and the OP is about 750,000+ lifetime rounds (according to an interview I saw awhile back).
Let's think realistically and understand that the OP is likely to never achieve that level of skill with a revolver. As mentioned by many people, a basic course is the place to start. The OP should try a variety of guns before the course if possible and ask the instructor to bring several revolvers and semi-autos to test. He or she should then attend a two day defensive pistol course using a rented gun. The OP will then have an idea of what is necessary in a defensive handgun. He or she will then know whether or not the small details of the tested guns will be advantageous or not.
Now, if the OP needs a gun quickly, then just get one. Schedule NRA Basic Pistol immediately. I tell people to buy a Ruger GP100 with 4" barrel if they want a revolver and a Glock 19 if they want a semi-automatic pistol. Both guns are very popular and can be sold with minimal financial loss if it turns out to be unacceptable for some reason.
Under no circumstances should the OP buy an S&W J-Frame or equivalent small revolver. Experts have difficulty shooting them; don't expect a positive learning experience with one. Buy one later after the OP knows what he or she is doing.
Budget at least $1,000 to the project because the gun is only part of the rig. The OP will need at least one concealment holster (lots of forward cant), a gun belt (just buy a Comp-Tac kydex reinforced belt), magazines or speed loaders, at least two ammo holders, cleaning gear, safety gear, practice ammunition, at least 200 rounds of defensive ammo, and tuition for class. Ammunition prices have skyrocketed since Sandy Hook, so $1,000 is likely low.
Finally, do not overthink caliber. Buy 9x19mm or 38 Special at a minimum. Go no heavier than 44 Magnum (but use 44 Special for personal defense) or 10mm. Stick with common calibers such as 9x19mm, 40 S&W, 357 Magnum, 45 ACP, 44 Special and so forth. Use ammoseek.com and ammoengine.com to find ammunition. The two "default" guns are chambered in 357 Magnum and 9x19mm. Both are fine for the purpose of self-defense with quality jacketed hollow point ammunition (though jacketed soft points in 357 Magnum should be fine too).