I would go with the longer barrel ...... S&W did make the 651 which was a kit gun type 22mag.
The link below shows a S&W 351 pd which can be had with a 3" barrel.

http://www.commandsurplus.com/product_info.php?products_id=76455&cPath=7293&source=googlebase

 

The 351PD can be had with a 3" barrel?? You sure your not thinking of the S&W317 .22lr.

 

I'd choose the 4 or even 6" barrel in .22 Magnum if at all possible. It is a blaster even at 6".

 

I'm going to finally get a .22wmr revolver to match my .22wmr rifles. Everyone tells me that the muzzle blast and flash is significant with the short barrel mags. Does it really matter if I get a 4" revolver vs a 2" barrel, or are both just as bad? I like the 2" for occasional carry, but I will get the 4" if the muzzle flash and bang is significantly reduced with the extra two inches so my wife and kids can use it.

I wish someone made a 3" lightweight revolver, like a S&W 317 in .22mag.

I have a Taurus 941SSUL like this: http://www.taurususa.com/products/product-details.cfm?id=371&category=Revolver which has a 2 inch barrel. I carry and shoot it often. I do not feel the muzzle blast is excessive. I submit that all other persons should be standing a safe distance behind the shooter and that the blast would not be an issue then.

 

I'm thinking more along the lines of bothering a new shooter. Internet lore tells me that shooting a .22wmr with a 2" barrel is like a cross between a flamethrower and a thunderclap

While I never seen one in person, I have watched some youtube videos of a guy shooting a NAA in .22mag and it does look that scary.

If a 4" is more tame, I stick with a Taurus 941 with a 4" barrel so my kids can use it. If it doesn't really matter (other than velocity) I rather get the S&W 351.

 

The .30 M-1 Carbine round in a pistol is similar. A rifle round in a handgun that is incredibly LOUD.