Here is the wirecutter discussion of the distinction for reference:
Starting in 2019, we began comparing dual- and single-hose models according to the same criteria, and we didn’t dismiss any models based on their hose count. Our research, however, ultimately steered us toward single-hose portable models—in part because so many newer models use this design. In fact, we found no compelling new double-hose models from major manufacturers in 2019 or 2020 (although a few new ones cropped up in 2021, including our new top pick). Owner reviews indicate that most people prefer single-hose models, too, since they’re easier to set up and don’t look quite as much like a giant octopus trash sculpture. Although our testing has shown that dual-hose models tend to outperform some single-hose units in extremely hot or muggy weather, the difference is usually minimal, and we don’t think it outweighs the convenience of a single hose.
The one major exception, however, is if you plan on setting up your portable AC in a room with a furnace or hot water heater or anything else that uses combustion. When a single-hose AC model forces air out through its exhaust hose, it can create negative pressure in the room. This produces a slight vacuum effect, which pulls in “infiltration air” from anywhere it can in order to equalize the pressure. In the presence of a gas-powered device such as a furnace, that negative pressure creates a backdraft or downdraft, which can cause the machine to malfunction—or worse, fill the room with gas fumes and carbon monoxide. We don’t think that most people plan to use their portable AC in such a room, but if your home is set up in such a way that you’re concerned about ventilation, skip the rest of our recommendations here and go straight for the Midea Duo MAP12S1TBL or another dual-hose model like the Whynter Elite ARC-122DS or Whynter Elite ARC-122DHP.
Here is the wirecutter discussion of the distinction for reference: