You're welcome. Yes, the memory usage during rendering process is the same. Let me add, that XRef Scenes objects within the external file are visible as a reference but cannot be selected, instead in case of XRef Objects depending on the object's XRef settings, you might or might not be able to edit the object’s entities such as its transforms, materials, manipulators, or modifiers.
Specially for complex scenes is generally recommendable to use references. Just take in mind, if you'll modify those referenced files, the scene containing those will be affected too. For this reason, a time ago we've decided to disable XRef for all bundled presets. There is a good reason for that: in this way we can modify these presets on Forest updates (i.e. optimize them, update materials, etc), while keeping the compatibility with existing scenes. If not, a same scene would look differently depending of the Forest version used.