AVI and MOV are software “wrappers” for a number of different CODECS. The CODECS and compression are largely what determines the quality of the file output. Without knowing which flavor of MOV you are using, it’s hard to say why the quality is low.
For a broadcast commercial spot your client should be requesting ‘uncompressed’ (even that is open to interpretation) files of some sort.
My suggestions: give them an AVI (uncompressed) and an MOV (PNG at 100% quality, = uncompressed), see if they have a preference. The PNG will be smaller; but it is lossless compression.
-jeff