I've never shot the 642 but I do own an LCR and I'm totally happy with it. I find it pretty accurate, very light, and overall I just really enjoy the gun.
I've owned/shot a 442 and a 642. Trigger on one leaves a bit to be desired, the other was GREAT - it had gone through S&W's pro shop. Never shot an LCR. That being said, the airweights are prettier than the LCR's.
I own three different rugers (none lcr) and think they generally put out fine stout weapons. Also have a 642 that I love. Sure trigger is a little heavy compared to a single action or striker pistol, but it's also really smooth. I'd go with it again over the lcr without a doubt, smith has a much longer proven reliable background with the j frames.
I'd go J-frame. You can order your 642 in a wide variety of finishes including the all-black PowerPort Pro Series model and the Mag-Na_Ported Barrel model. You can even order it with pink Hogue grips for your lady.
The LCR only comes in one basic version and a CT version.
Plus, J-frames have been around since dirt. Their record for durability is legendary. Ruger makes fine weapons, but the LCR needs to be around longer for me to trust it like I would a J-frame.