convertxtodvd vs amadis

ok i have a question i use both of theses programs to convert x264 movies to dvd format ok when i use amadis i get 1 file and it is smaller i did convert predator 1985 original file was x264- 4.4 gig after conversion to dvd5 amadis final convesion was 3.1 gig and convertxtodvd was 4.8 gig so which 1 is better and how can i improve my picture quality do i have to have bigger compression to dvd9 or what to get better picture quality and convertxtodvd conversion was in 5 files but amadis in 1 file which i better but still how to improve the picture qualit or is there a better software for x264 converssion also i watch it on my HD upconverter conected to HDMI and than my tv