Ruger did the sigle action Blackhawk in .38/ with a 9mm cylinder .357. With the rod exctractor, no clips were needed.
Ruger did the Service-six and Speed-six in 9mm. These required the clips to work.
Ruger did the SP-101 in 9mm. This also required clips.
Taurus makes the 908?, which is a small-frame, 5-shot. It requires clips.
Smith and Wesson did the 940?, which was a J-frame, 5-shot. It required clips.
Smith and Wesson did the 547, which was a K-frame with a special extractor that didn't require clips.
I own a 3" 547 (they came in 4" as well). There's really no difference between the 547 and a model 13 other than caliber, special grips on the 3", and a special hammer (semi-bobbed). The extractor is a unique design that allows it to work on rimless cases. Other than that, it's the same as any other K-frame.
Power wise the 9mm sits between a .38 spl +p and the .357 mag when in a revovler (based on chrono tests with same type guns in different chamberings, and doing the math for energy). Recoil is in the middle as well. Accuracy is supurb with the 9mm. Some say it's because of the efficent bullets used in a 9mm, or the efficient case size, I dunno, but mine drives tacks better than it has a right to. S&W revovlers are usually no slouches in the accuracy department, but my 547 is exceptional. Other 547 owners I've talked to have had similar results.
There is a great variety of 9mm ammo you can take advantage of, since you don't have to worry about cycling an action, and there's a wide variety of 9mm made, because of it's popularity in autos. Reloading it can be interesting as well, again because you don't have to worry about feeding. The 9mm case is very short compared to the .38/.357 and extracts completely with ease in even small revolvers. Much better than a .357 case does.
It seems back asswards to put a 9mm into a revovler, but it's really not a bad choice. Better performance, than a .38, wider selection of ammo, and easy extraction in even belly-guns. I think they lack popularity because people can't mentally make the jump to using 9mm in a revovler. Botht he Ruger Service/Speed-six and S&W 547 were originally built for European police use. The surplus was simply sold off here, but never took off. However, anyone who actually has one seems to like the arrangement very much (including me).
I think alot of people figure they would only want a 9mm if it were hi-cap, otherwise they'll take a .45. To put a 9mm in a six-shooter doesn't make sense to them, but in reality it makes more sense than using a .38 in some cases. Except for the 547, and the Blackhawk, you have to use clips, and clips can be more difficult to manage no matter what caliber it is. That's a big strike against it's popularity.
I'll probably buy a 4" 547 to go along with the 3" someday (but they aren't cheap). I've given serious consideration to a 2 7/8" Ruger 9mm, as they are much cheaper. I think I'll probably try out a Taurus first though, as it's still in production and the 9mm in a snubbie is pretty hot.
9mm in a wheel-gun sounds odd, but it's a pretty nice set-up actually. If you are in the Tidewater area, or are going to the BRD, let me know and you can shoot mine and see what you think.
Ross