I prefer to look at still pictures while I'm masturbating. There are exceptions but videos of other people having sex either with themselves or others quickly run out of interest with few exceptions. But I would certainly watch a video of someone filmed secretly while masturbating (or fucking for that matter). The difference would be the naturalness of their behaviour and one's own rôle as a voyeur making you an unwitting (for them) part of the scenario. That's better than being a spectator watching a sex scene filmed by a third party. It's the moans of pleasure and facial expressions (and curses in the case of men) of people masturbating while they think they're unobserved that make it so exciting and real. Of course, guys look pretty stupid when they're masturbating but let's face it, people thrashing around having sex do but that's also a key part of the excitement - one person, the masturbator, letting go and revealing his or her secret self while the other, the watcher, coolly observes. There's an element of humiliation or self-humiliation for the masturbator and I like that.