Well I'll play Devil's advocate here and go with Porn Stars. Why? 1. Amateurs don't care about or don't know how to go about making the fucking look good, 2. The camera angles with amateurs suck and almost always feature either only the penetration or just faces, but not both simultaneously. 3. The lighting on amateur vids is terrible 4. Amateurs are often not well-kept physically and hair-wise 5. Amateurs don't have boob-jobs as often (I know many guys find these a turn-off anyway) 6. Most amateur sex only features one or two positions 7. The dicks usually aren't as big 8. The girls are often less aggressive
Yes, overwhelmingly the action with amateur stuff is more real, but usually that means two bodies pressed together and kissing, and to me that is romance stuff to be experienced in real life as opposed to the pure lustful stuff that I want to see on video (plus there are also times in porn when there is especially good chemistry between the pro couple).
Ideally, the best compromise would be a hot amateur couple: girl is a gorgeous nympho, guy is super well-hung, they are more in-lust than in-love, both major exhibitionists, and would agree to be shot with pro lighting/positions/camera angles because it would turn them on to have the world witness one of their epic fucks in full pro porn effect.