It really depends, because if both are done well, they both can be enjoyable and arousing. And both do have their advantages, hentai can make beautiful girls, large breasts, and makes usually some of the more disgusting kinks(in my mind) like anal fisting seem not so disturbing(at least in my mind), because it's drawn and animated, but live action has that realism to it, and while they all not might have the qualities as the hentai girls, realism makes things seem more enjoyable for me.
Hentai also has that ability to make fictional fandom characters engaging in sex seem more real and enjoyable to watch, as when I watch real action fandom pairings, I just think fetish cosplay.
But yeah, both have their ups and downs, but in my mind, real action is the one I watch the most of, and I think it's better, but hey, I just watch softcore lesbian vids on xHamster(I am also very picky), so what do I know?