i prefer natural, no matter if they are "solid" or hang a bit. Just my personal preference - others may have a different one or none at all.
i once had a ONS with a Woman who had two different sizes, like C cup and D cup. She was very shy and nervous when we were getting out of our clothes. But once in the nude, i commented that she had a great body. Then she directly asked about her tits and if it would not be a problem they were not equally cupped. i just said, "Bigger tits are great and smaller tits are great, each for different reasons. I haven't seen one Woman yet whose both tits had been exactly equal. You've got the best of two worlds, be proud of them!" And that was no lie but how i felt. Then i went on sucking one nipple and felt it hardening while cupping her other breast with one of my hands. i really liked them alot.