I'd said it's a case of what I prefer as I don't think there is a requirement per say. Both the Pearl and the Panasonic (more so the Pearl) overall images just came across as dull (dim). On top of that the whites didn't have any pop on predominately dark images. Which was still evident in other mixed content images.
The RS1 and HD80 had lots more brightness on both conditions. It felt like you were straining to view the images especially after viewing the others.
Regarding projectors being defective I can only go by what I received. I checked out five different projectors but ended up looking at ten different units trying to find a good one on everyone of them except for one which was good from the get go.
At some point you have to accept they are what they are or do you think after three units you should go for a fourth? I went as far as three with one projector I really wanted to like it.