Since I am environmentally conscious I am going to recycle from some of my previous replies
If you ask 3 guys this question you will get 6 different answers
As far as content is concerned I'm a creature of impulse. I have purchased all kinds of video, from the simply flirtatious to all out (or more accurately, all in) explicit intercourse content. Maybe it's related to something in the water or the phase of the moon but I tend to mix it up a bit. As long as what is going on is genuinely depicting a model's inner feelings there is a good chance it will resonate with me no matter what the context is. Similarly, if the model isn't "feeling it" it can come through in the video. That's not a good place to be for her (or for us).
Audio is important. Videos offer an opportunity for aural stimulation which pictures cannot. Words or sounds can amplify the video experience to a whole new level of intimacy.
Fetish content can also be an enticement, although since there are literally dozens of them there are no certainties about what will hit and miss. It's one of those things which will either click or not ... at least it is a good excuse for experimenting!
Hope some of these ramblings help!