10,000 x 1 (720p) vs 1,000 x 1(1080p)

Contrast ratio is a meaningless term when used to compare different makes. There's no set standard they all use, so the numbers are useless, unless comparing two current models from the same manufacture.

At only 47" and 50" there will not be a huge difference between 1080p and 720p from these brands. I would view both, playing with the set up to suit your preferences and choose which one looks better in your opinion because that's the only one that matters...