It's a spectrum rather than two categories, and most ships sit somewhere in the middle. Expedition-leaning operators prioritise getting you outside as much as safely possible, run split landings, and will still operate in wet and splashy conditions. Luxury-leaning operators prioritise comfort, may skip marginal weather in favour of the spa or a film, and often run one group at a time with more waiting aboard. The gap in time off the ship is the part people underestimate: up to about six hours a day at one end, sometimes around one hour at the other.
The practical rule that falls out of this: if maximising time off the ship is your goal, you need both a ship of 199 passengers or fewer and a hybrid or expedition-leaning operator. One without the other doesn't get you there.
Hybrids are where most people land. Four or five star service with a real expedition underneath.
A genuine six star experience does trade away expedition time, and that's a legitimate thing to want. Someone who wants excellent food, a quiet ship and a comfortable week with some Antarctic scenery should buy that honestly rather than be talked into a hard-charging expedition they won't enjoy. What causes bad trips is buying one while expecting the other.