just bought a 43" pioneer so I'd share some of my thoughts.
first I was offered the PDP435 which is the previous model. I have no issue with it as I know the improvements of the new models would not be obvious once you get the TV home. also the old model was being sold at a good discount, even Audio House cannot match.
Drawback (or so I thought) was that Pioneers have an external tuner, so you have one extra box to find a place for. vs Panasonic, which I thought the colour was slightly more neutral, had a built in tuner and better speakers. unfortunately there are no "previous" models of Panasonic so it is a $1000 premium over the PDP435.
Only after installation did I realise that the Pioneer was much more practical. the tuner with all the mess of cables can be hidden below or on the cabinet (if you have a cabinet). with the panasonic all the cables will have to fly up to the TV along the wall, not pretty.
The older pioneer also has an HDMI input and I think 13xx x 768 pixels, guess it is HD compatible?