Okay, this command line will work with maps:
UE4Editor StrategyGame -run=PkgInfoCommandlet …/…/…/Samples/Games/StrategyGame/Content/Maps/TowerDefenseMap.umap -exports > Exports.txt
(Fix up for your map, naturally). You can Add -simple before the > Exports.txt bit to see a simple format (which you can use with Excel to sort by the size column).
Josh