This product is so comfortable and soft!! It's not as lifting as a typical bra or even a wireless one with an elastic, but it makes my chest feel weightless. That's saying a lot given that I'm a 32DDD. I initially went with a medium based on the size chart, since I worried the large would be too loose at the band. However, the medium juuuuuust covered my breasts, and would often ride up and expose a small part of the underboob. So in my next order I decided to get a large, and it was absolutely the right decision! It completely covers my chest and the bottom "band" is actually underneath supporting my breasts.
In conclusion, if you notice that it rides up, you'll likely benefit from sizing up. For reference, I have 32DDD sized breasts and am happiest with a large.