RG is junk, or is it? Not to be rude, I'm just asking for clarification. If someone actually likes them, I might pick one up.
I have an RG40 .38 special. It was my first handgun.
Mine has always worked well, and is as accurate as the person shooting it. Despite what some say, it stands up to +P ammo just fine.
These guns seem to function, but are not meant to be a shoot-every-day type of gun. You buy it, make sure it works, and run a cylinder or two through it every month to keep proficient, and when you need it, it will be there for you.
Ive handled several of the rimfire RG and other cheap german import revolvers. They don't hold up nearly as well as the centerfire versions, but if you find a working one, they usually at least spit most of the lead out of the front when you fire them. With that said, only the rimfire versions are any smaller than a J frame anyway.
As far as top break revolvers, for a defensive firearm you want something made in the 1900's (unless you hand load blackpowder rounds), preferably a Smith and Wesson or a Third Model Iver Johnson in .38 S&W, in good mechanical condition and preferring an intact nickle finish to resist rusting.
A good rule of thumb for whether or not you can fire smokeless loads in a particular top break, is if while the gun is not cocked, with the trigger forward, the cylinder spins freely in one direction. This is due to the older cylinder indexing cuts on most blackpowder era top break revolvers.