A lot of people get the .22lr in the same barrel length as other revolvers that they have, me included.
I have mostly 4 inch revolvers and having the Mod 18 allows me to have the same feel in practice as shooting my other 4 inchers at a much lower cost. If I had more 6 inch guns I may be tempted to to get a Mod 17. Of course I do have a 6" Mod 19, looks like I need to get the 17.