There is a big difference between the bluray version and the dvd I heard that there is not much, is that true?

@surume: They basically kept the 480p resolution from the original source, instead of doing an upscale (like some old school anime being released in BD do). However, quality improved a lot. You can check the comparison between DVD and Bluray here: https://screenshotcomparison.com/comparison/25596 As for this 720p version, it is an upscale for those who would rather watch a larger resolution than sticking with the most pristine version. Regardless, I believe we managed to preserver the quality very well when doing this upscale.