To talk technical, the pointy end and the blunt end will both rock the same. If the boat is rolling,i.e., tilting from side to side, the pointy part, blunt part, and fat part will all roll the same. But the bottom floors will roll a little less that the top floors. If the boat is pitching, diving and rising end to end, the pointy end and the blunt end has to move the same amount. When one end goes down the other end goes up, unless the boat is hinged in the middle. The fat part will not pitch as much as the ends. So the lowest floor in the fat part on the boat has the least movement. Do you think that's why the crew lives there?
End of technical talk.
Today's ships all have stabilizers which holds the ships movement to a minimum even in fairly rough weather and seas. And satellite weather and radar allow the ship to avoid bad weather and rough seas for the most part.
While it is correct that the lower decks midships are the most stable, its only a tiny difference. And the wind and waves will rarely be coming at the ship straight from the side or straight from the bow. Almost always the seas will be quarting, coming at the ship at an angle causing pitching and rolling together. This makes it seem worse than it actually is because so many people find that to be a little scary. Which makes them feel seasick faster. Just take some Bonine, available at any pharmacy, along with you and don't hide in your cabin if you start to feel woosy. Get up on an outside deck, breath some fresh air and look out to the horizon.
Have a good time
Dan