region 1 vs region 2 file sizes

[gunner89]

Hi, im ripping my tv show dvd's (originally bought) using dvd decryptor to create the .vob file, then i use ps3 video 9 to create a .mp4, using the 1080p 2 pass option, this produces 350mb files for my Region 1 dvd, however when i try and do my region 2 dvd's of the same tv show and the same running time, the same settings give me a file size of 600mb, any ideas why?

I know ntsc is 720x480 and pal is 720x576 but surely that wouldnt double the file size?

Thanks