I have looked a lot at both the Panny and the LG (Zenith) Sets and I too was very interested in the stretch modes for SD. Here are the modes that each has:
Normal - 4:3 with black bars on the sides
Full - Stretches evenly across the screen. This is the one that makes people look short and stocky.
Zoom - Zooms into the center to fill the screen, but cuts off about 20% of the original image on the top and bottom
Just - Stretches only the outer edges of the image but leaves the center of the screen in standard proportions. This is fine for most SD TV. When watching sports it can get annoying, and any stations that have text bars acorss the screen (like ESPN or CNN) don't look right with the Just stretch.
The LG and Zenith Sets have the following modes:
4:3 - same as above, black bars on the sides
Wide - evenly stretches across the screen
Panorama - same as the "Just" on the Panny
Zoom1 - Same as the Zoom on the Panny
Zoom2 - In my opinion, this is the best out of all of them. It stretches the image to fill the sides just like the Zoom, but it also stretches the top and bottom slightly. You do still lose some of the image just like on regular zoom, but only about 10% instead of like 20% of the image. it greatly minimizes the "stretch" look and fills the set quite nicely.
Now all that being said, I love the stretch modes better in the LG sets, but I think the Panny has better picture quality. I still haven't made up my mind either, but as of now I am leaning towards the Panny. I figure as time goes on, more and more content will be HD and then I will rather have the PQ over the SD Stretch modes. Also, I have noticed that a lot of new shows in SD are in widescreen (like ER or the West Wing on NBC). The put black bars on the top and bottom, so if you did a standard Zoom, all you are losing is the black bars, not any of the image you want to watch. Just my $.02