If you had to choose...

I have The Guide to Female Orgasms and while it's decent as a porn flick, I haven't learned that much about orgasms. Perhaps the G-Spot Guide will be more specific and informative.

I have the Expert Guide to Female orgasms, and I think it's great. It really depends on how much knowledge you already have on the subject. I found I didn't learn much, but my knowledge base on the female orgasm was already quite broad. I've read a lot of books and did a lot of online research over the years. That being said, my man didn't know anything about the female anatomy or the different types of orgasms women can have. Tristan's explanation of the arousal cycle was most informative for him, and helped him understand things better. If you are looking for more specific information on the G-spot in particular, I would say to get the G-Spot Guide. I haven't seen this one yet, but I'm sure it will go into that area more in depth. Just depends on what you are looking for. What I got most out of the Expert Guide to Female Orgasm is that you aren't just reading about techniques, but you are shown with diagrams and actual sex. I especially liked seeing certain toys in action, and it answered a lot of my questions as to how they would actually work in the bedroom during intercourse.

I would like to comment on Tristan's work to a broader degree, but I've only watched this one video. Perhaps the others are able to polish the edges around a holistic tour through the various sexual arenas that this video was not able to do.