What are the differences between JD Robb and Nora Roberts?

I know they are the same person, just writing different genres. But what are the differences? I think I've heard that Nora Roberts is more romantic, and JD Robb is more action/mystery. Is that right? I'm not sure if I would like her. I don't mind some romance, not nothing that is "hot and steamy." I like to have some left to my imagination. My favorite authors are Nicholas Sparks, Richard Paul Evans, and Janet Evanovich. Normally Evanovich is a little more sex than I would l like to read about, but she does it in a comical way so it makes me laugh. Any suggestions for JD Robb/Nora Roberts books?