I stood in harvey norman and looked at tv's. Right next to each other was 1080P 50" 200hz but one was brighter?

I was in harvey norman checkin out tv's im not sure weather they where plasma or LCD's, but there where right next to each other, and one looked a lot brighter and a lot clearer than the one next to it, the one next to it was darker and slightly duller. But they where both 200hz and 1980*1080P resolution. What could it be?