42" Lcd 1080p or 50" Plasma 1080i?

I have the Sharp LCD, and my father wants to trade me for his Panasonic Plasma. The distance is just right for either a 50 or a 42, I watch a lot of TV (some HD satellite, Blu-Rays, SD TV), also play games often. There is no problem with direct sunlight. Both models are pretty old, the LCD being the 60hz kind and plasma being in the day where only rich people had them.

Suggestion:

Most TV broadcasts are 1080i, so you're not likely to see any difference between 1080i and 1080p unless you're watching Blu-Ray discs. Even then, you probably won't see a significant difference on that size screen at a normal viewing distance. Plasma TVs generally have higher contrast ratios than LCD TVs, and according to Consumer Reports, contrast makes more difference than resolution in the image quality. I wouldn't hesitate to take the 50" Panasonic if it's in good working order.