The best advice is to view them side-by-side and buy what you like. In my opinion the video world is changing and Samsung is becoming the leader in both plasmas and LCDs. Samsung is the largest electronics company in the world and they have made tremendous strides and are dedicating lots of resources to their plasma offerings. The HPS 53 and 73 series is only 6 months old. The Panasonic series (60U) is exactly what they were offering 18 months ago with no enhancements. Samsung offers their customers 2 forms of burn-in protection, but Panny offers nothing. Samsung offers a modern piano black housing while Panasonic offers a silver housing which looks like it was made by Mattel.
From a picture quality standpoint, the Samsung offers a clearer, crisper picture. View them side-by-side and you will see more detail in the Samsung. Additionally, stand 3 feet from both sets and you will see less pixelation, screen door effect, noise and artifacts on the Samsung. Look at the coloring on people's faces and you will see the infamous panasonic clay face. The problem was so bad that Panasonic had to develop a firmware update to correct the problem. Unfortunately, the average consumer doesn't know how to download and install a firmware upgrade. Again, Panasonic is offering 18 month old technology which is a lifetime in the plasma market.
Ask the store salespeople which are the best selling sets and they will say the Samsungs are flying off the shelves. Panasonic has been hurt by Samsung and has had to drop their prices dramatically to compete. If you have the best product you don't have to drop your prices to compete. The world is changing and a lot of people are having a hard time beleiving that Panasonic is no longer the leader.