depends on what codec or format you want to use, all have advantages and disadvantages
sounds like you dont know what your doing and used the wrong codec or none at all to make the file 3 times bigger
these days, for all around use, one of the mpeg4 family of codecs work as good as any--divx, xvid, or any of the other mpeg4s like the open source lavc or opendivx work fine too