Unders and overs do look different yes, unders give a more sloped and natural look whilst overs are rounder and look more *augmented*. Also when Drs talk about unders they are referring to partials, it’s very rare for any Drs to perform full unders anymore so when they say unders they mean the top under and the bottom over.
They each come with advantages and disavantages, unders look more natural and take longer to sag but the op is far more painful and most people don’t full regain the use of muscles (slight discomfort/muscle distortion). Overs are more likely to ripple and you have to wear very good bras/sleep in sports bras to stop them looking like golf balls in a sock :p They are generally rounder, softer and more comfy in general.
It’s all about deciding what you want to achieve and weighing the pros and cons for you personally.
