The window unit!
In order to do its job an AC unit has to pass air over its hot coils to shed the heat it's removing from the living space.
With a portable unit, that air comes from INSIDE your room, which the unit had just got done cooling, and then throws it OUTSIDE! Which creates a low-pressure condition inside your home, which causes warm, moist air to get sucked in through the cracks and crevices, which the unit then has to cool again. Portable units are not efficient at all, regardless of how they're rated. It may have a rating that looks pretty good, but it disregards this crucial fact of how it works, in that it wastes a lot of its own cooling power.
Window units, on the other hand, keep their own entire hot end outside from the beginning. You lose some window space but they are far more effective.
Neither of these can hold a candle to an even middlin-fair mini split system.
Mini splits are available in sizes down to about that of a window unit, but the entire hot end of the system is completely outside and attached via piping, like a whole-house central split system. The noise of the outside unit is completely on the other side of the wall - not necessarily close to a window, either, since the piping goes through a hole only about 3" wide and thoroughly sealed up after installation - and the inner unit is pretty quiet, especially once it's hit the set temperature and slowed down to a maintenance level. Mini splits are available with SEER as high as 30 - no window unit has ever gotten anywhere close to that. That's air conditioning for super cheap, friends.