What is the difference between avi and mov

Hi FCP users,

I am actually an audio guy, but I would like an answer on something.

I work with Logic, and usually use quicktime movies when I am working to movies. But I am working with a client who is an Avid user and swears by avi files. Can someone explain to me the difference. My client explained to me that avi's are better than mov files. He claims their file sizes are bigger, so therefore there quality is better. He said there is some form of compression on quicktime movies which lessen the quality to avi, even if the mov is uncompressed apparently the quality is still less than an uncompressed avi. If this is not true, could someone give me the real big difference between the two.

I thought is was more of a preference, like windows users prefer wav, and apple users like quicktime movies. Like with audio, there isnt a huge difference between aif and wav. Windows users prefer wav and apple users aif.

Thanks in advance for any information.