mac or pc?
the compressing program wont make the file any smaller, it is the codec that will actually decide how the video will turn out. (im pretty sure, but not 100%)
if your on a mac, try and get mpegstreamclip and try to find the codecs that it says it doesnt come with. it works pretty well. i usually export to h.264, but that gives somewhat large file sizes. this of course depends on if your original shot is high resolution or not...