--What do you carry now, and how (pocket carry, IWB, OWB, etc)?
--How do you plan to carry the LCP or LCR?
--What have you shot before, and (in gereral terms) what do you like, revolvers or semi auto pistols?
If you get a chance to try (shoot) either or both, do so. If not, see if a gun shop will let you try and stuff each in a pocket.
For me, the LCP is a true pocket pistol. I own one (actually I have owned two...long story, but they both work/ed perfectly).
I have not owned an LCR, but have owned about a half-dozen J-frames, and the LCR is very similar in size/weight to the J-frame. The LCR/J-frame is a fair bit longer front-to-back, and while I have pocket carried them, the grip tends to "peek" out of the top of my pocket with jeans or dress pants. For that reason, I consider a J-frame more suited to IWB carry...and if I am going to carry IWB, I will carry something larger.
Once again, try (if possible) before you buy. Good luck, and please tell us what you decide and how happy you are with your choice.
We are living in a truly remarkable time--we have so many good (and affordable) choices available, and concealed carry permits are both easier to get and more popular than ever.