Running Refrigerant Line Outside vs. Inside

So we have to run lines about 15 feet along length of house before going turning and directing toward system.

The HVAC guy said efficiency probably will only marginally hit if they are outside. The AC unit is under a second story deck (outside edge) so enough space. I want to nail sheetrock to walkout basement floor joists sometime soon so if he throws the lines inside then along the wall, they will have to be exposed inside. So thinking running them outside under deck / against exterior wall before running inside into the utility room is going to be better in that regard.

Any downsides to running outside like that?

submitted by /u/JayReddt
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