Some Barths have a rear window---some don't!!

What are the advantages/disadvantages??

Mine has the rear window and the advantage of being able to see the trailer that I pull. Can't see it from the side mirrors because it is too narrow but can see the ramp/tailgate through the back window.

Have not found a disadvantage.

The Breakaway I had (now Turtle's) was ordered by Dr. Yale with a rear window. seems atypical for a diesel pusher. I think one of the Barths recently in sightings or for sale was likewise.
On my trip to CA and back, I was SO GLAD to have the back window. Although the window was very high (could barely see roof of MINI on Featherlite trailer), I could see traffic behind me. It was like driving a van on steroids rather than a box truck. I had a wide angle lens on it, so as to have some vision close behind.
I see no disadvantage. It was nice to have the large window behind the pillows when I was in bed. At night I closed the blinds, but left a gap at the bottom to peek out. When driving, I had to remember to move pillows out of the line-of-sight to rearview mirror.