In real life, it takes longer to clean a room working around the furniture then if the room was empty and there was more space to clean.
So, if work and time needed is the criteria, you should charge more for cleaning around the furniture. And if you don't, you're discounting your work. Which is fine, if that's what you want to do.
It is more of how you like to handle it and how much resistance you get from your clients for not "deducting" the furniture space.
Also in a way, it is about how your client perceive your business.
Unlike Mike I charge for the full size of the room. I use the same logic throughout my business- It takes me longer, I charge more. It takes me less, I charge less. And it allows me to screen certain clients.
In 26 years in business, I can recall only one client I lost because of it. From the way she sounded, I think it was my gain.