How I watch porn is two fold.
1. Fascination - stuff that I'll never do but I need to verify that people are actually doing it to satisfy my twisted curiosity. For example : Gangbangs, atm, snowballing, anal,extreme bdsm, etc... For me it's the equivalent of watching 4chan videos or clicking spoilers despite the warnings not to.
2. Arousal - stuff that I know works for getting me off when I ladyfap. This would include more scenario based work . I like a believable plot with a solid attempt at acting, lol. I've never watched amateur though.. I think I prefer the theatrical fantasy aspect of it all.