Portable would be with a hose. If it has an air inlet hose and an air outlet hose, it shouldn't create a vacuum. A single air hose is the worst.
I have had a "portable" (floor standing) unit that would shut itself off for a thermal overload. When the exhaust hose was shortened to a straight 2' run, it quit overheating. It was a big one, 10k+ btu. My 5k btu window unit does just as good of a job.
Units with a hose will list a total btu, and another value. That's how much is lost with the hoses.
A mini split won't have these losses.
If I were choosing between a window unit, or a hose-unit, I would get a window unit. Best output per watt, aside from maybe a nice mini split.