Right here, fyi:
Philips 42" $4500... Since he gave the model #s, it really is quite easy to find out for yourself...
To attempt an answer dblan's question, the difference is probably in the quality of the panels from the manufacturer - fewer defective pixels, better "real" contrast ratio, as opposed to the "dynamic" ones that the Panasonic claims, etc. One factor might be that the Panasonic is a higher resolution set than the Philips, so it has more trouble redrawing the screen between frames than the Philips does. Being smallish sets, the lower resolution of the Philips isn't noticeable and the higher quality makes more of a difference.
Someone else probably has a bit more technical knowledge than be as to the differences. It is very likely that the Philips does have the better picture, as we're not necessarily comparing the top model for both brands, but that is also a hard thing to know without seeing them both side by side.