Not a huge fan of either, but a boob job is definitely preferable since they can look a lot more convincing. Not to mention getting a nicer ass is a lot more attainable for people, whereas you can't really do anything about tits, lmao
Not a fan of either but would have to go with breast augmentation, I've seen some vids on the hub with the actresses having fake asses and it looks way more noticable and distracting, kills the vibe for me