Unlike Sex Magic, which has plenty of nudity of all kinds, The Orgasm Diaries concentrates its bared skin on sexual acts, including a couple of self pleasure scenes, and one memorable act with a popsicle. This one did venture further towards softcore porn that the first film, but also had a developed plot. However, it was a bit too slow moving for my taste, and dragged quite a bit in the middle section.
As far as the acting, like most documentaries, it's hard to tell how much was going on in Sex Magic. I find no fault with either of the leads in The Orgasm Diaries either. Both were certainly capable of handling the material, which felt very professional, and not at all amateurish. Sure, the characters may have been amateurs in some way, but the two people inhabiting Noon and Manchester really made them come to life. If the direction had been more of a documentary style, and not so obviously a movie, I'd probably be more inclined to believe they were real than I do Dez. Not that I'm suggesting The Orgasm Diaries would have worked better that way; rather, I am praising the actors for breathing such life into the parts.
Neither film is what I would call groundbreaking or amazing, but neither is a total dud either. If you enjoyed Real Sex, watch Sex Magic. If you like indie films that have more nudity than would be allowed in an R rated theater run, watch The Orgasm Diaries. Both are available from IFC.