Panasonic's PQ is better than Samsung's. Colors and the picture itself is more realistic than the Samsung's somewhat aesthetic.
Picture quality can be quite subjective. If the Panasonic's picture appeals to you, then by all means go for it. With the default settings, the Samsung's picture would be rich on the reds. The Panasonic on the other hand would have dominant greens.
The Samsung's main advantages are RGB controls (allowing you to calibrate the image to a more proper color balance), better contrast, deeper blacks, finer shadow detail, higher motion resolution and lower power consumption (aside from being slightly larger). The Panasonic's main advantages are good deinterlacing and 24Hz cadence, together with a fairly good reputation for reliability.
I've been a Panasonic plasma and lcd user for sometime now. They've been quite durable in my experience, save for some problems here and there. I just feel that Samsung has the stronger product at this price point from the image quality standpoint.