Both portables exaust through ducting to the outside.
Sheldon Koehler and I just had this discussion a few weeks ago.
An external a/c is designed to shed energy through the (external) air forced across the condenser.
An internal a/c would seem to want an external inlet and external outlet, while recirculating the cooled air. ie, two air flows:
1. it sucks in cooled room air, cools it more, and returns it to the room.
2. suck in external air, forces it across the much hotter condenser, cooling liquid in the condenser, and exhausts the (room's heat) back to external.
If you don't have 2, then you're sucking in hotter-than-room air into the room on top of the equipment's heat, and you're asking your a/c to do a LOT more $$$work and with less cooling results.
You can prove this in your car by feeling the temp a/c vent when the a/c is on fresh and recirculate. The recirculate temp is much lower.
Len
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