Not a Ruger, but I have a S&W 642-1 that has been my ankle gun for years. I purchased a converted 9mm cylinder on the EE, and had it fitted to that revolver (dual calibers, with cylinder swap). I've been very happy with it, and it does come in well under the .357 LCR's weight (my father owns one).
Recoil is so subjective that I really don't say one round shoots lighter than another anymore... but I did not have any problems transitioning to the 9mm in regards to recoil. I felt standard pressure 9mm (UMC 115 grain) shot easier than standard pressure .38 Special, which I used to use for practice. I'm not really interested in shooting 9mm +P out of an alloy revolver, but I've talked to people who have done the same conversion, and they did. My carry load for it will be Hornady 147 grain XTP.
Accuracy was fine out of the .38 barrel. Within the first 50 rounds, I was able to do a 2" group at 15 yards... so I shouldn't have any issue with qualifications with practice. The only thing that really will be a big change is moon clips over HKS speedloaders, but I doubt that I'll have major problems. The trigger and controls being identical really is making the transition easier. My other option was a LCR in 9mm, but didn't want to go through the hassle of a new gun/holsters/training, and still have a DAO revolver. If they made a LCRx in 9mm, I probably would have bit the bullet.
The LCR is a very good revolver, and if I didn't have so much invested in the S&W (as mentioned, gear is a part... but training is like 80% of my reasoning; I've been shooting it since mid-2009), I'd definitely would go into it. Whether it is a 9mm, .38, or .357... that depends on you. If you are going just looking to deplete your 9mm ammo, with no intentions of keeping it fed afterwards, get a Glock 19 and shoot the hell out of it before selling it. If you are going to keep it in rotation and fed, it is a very good pistol in 9mm or the traditional revolver calibers. For me, I like magnum calibers... but not a fan of .357 Magnum (I don't think the gains over .38 are worth it... unlike the gains of .44 Magnum over .44 Special... but that is another subject on its own). That is why I went with an Airweight J-frame in .38 Special. If I was in the same boat, I'd opt for 9mm... but I also am issued a 9mm sidearm (and have a SIG P938 as another backup gun). 9mm is so easy to get, and there are plenty of different loads available for specific needs. .38 is similar, but it also started life as a black powder cartridge... which is why you have a round longer than a 9mm, but with barely equal or less power.