The "P" has an HD3 chip and a 3rd generation light engine. It's HD ready, but has no digital tuner.
The "R" has an improved faster chip and a 5th generation light engine. It's taking the place of the 63 and has the digital tuner. Also, it's a floating screen design.
Just bought the R6167 myself. The "other" difference between the 2 TV's are the "P" version is the 2004 model while the "R" version is the newer, 2005 model.