Nope, they are both .jpg, and even the second file has lower resolution (960x768, compared to the first which is 1029x823)! And PNG is generally larger filesize than JPG. So you're kind-of wrong on both accounts :P
I kind of expected 1280x1024 at least. PNG of course.
However I resized this to 500x400 for the splash. I do like it, but I really hoped for a high-quality 1280x1024 wallpaper
(without PRO HD as Mercado asked for
)