Avi2dvd vs convertxtodvd4. opinions wanted


I am curious to know which out of these 2 programs is the best. So far, I cant notice a difference in quality.
But I do notice that from a 700-800 mb avi file, convertxtodvd 4 only produces about 1.5-1.8 gb of movie, where as avi2dvd produces 4.3 gb.
Does that mean that convertxtodvd is converting to a different format? or it loses quality?

So far I dont notice a difference, I’m just wondering which program is better? I do the convert then I burn with imgburn.