A well-furnished and comfy apartment as in like someone actually lives there (whether true or not).
This has been my biggest knock against the incall agencies like Euphoria and XO in the past. Many times I went, the apartment was sparsely furnished and the bed just had 1 sheet, screaming "high volume incall". The agencies have great talent, but the other half of the equation is the ambience of the setting. Take a girl who is a 9 and an apartment that's a 5 and the overall experience is a 7. Whereas with an outcall furnished to my liking I can keep the entire experience at a 9.
Great topic.