I had an S&W 442 that I willingly traded away after getting the LCR.
Trigger -- The LCR is much better. Its lighter and smoother; I can get groups with it. With the 442, I could hit the target in lots of different places. The 442 trigger really soured me on an otherwise fabulous snubnose.
Sights -- Standard sights on the LCR are a little more visible. The bigger dot option is even better if you get that model (I didn't because I bought my LCR before the bigger dot was available).
Finish -- I haven't had any issue with either the 442 or LCR. A j-frame in stainless (like a 642) would negate the issue.
Weight -- The LCR is lighter by a couple of ounces -- enough to notice a difference when carrying.
Recoil -- The LCR is noticeably more comfortable to shoot. The Hogue grips make .38 +P loads very manageable. A cylinder of .38 +P in the 442 was enough for me.
Grips -- More options for a j-frame. The stock grip makes front pocket or ankle carry really easy. I got the larger factory grip so I could get all of my fingers on it, and I really liked the grip, but it did limit pocket carry. The LCR has two options. I've only used the standard, but there is a smaller, smoother grip now available.
Pocket carry -- I'd give it to the j-frame with stock grips for pocket carry; it's shorter and smoother in the pocket. The standard LCR grips are a little thicker, longer and "tackier" in a way that makes drawing it from a pants pocket a bit tougher. With the longer grip on the 442, I liked sticking it in a back jeans pocket -- very easy to draw. With the LCR, the grips can hang up because of the Hogue texture -- I stick with IWB.
For pocket carry, I'm not as much a fan of the LCR -- there are lots of other guns that will pocket carry better in my opinion -- but I prefer the LCR so much that I'm willing to go to IWB and dress accordingly.