One problem I've found I have with AVI files is that the audio of the file almost always coming out with a very tinny, almost metallic sound. One alternative I used to work with was MPG, back a few years ago when I downloaded a bunch of Chipmunk episodes off YouTube because I foresaw them being taken down eventually (by Warner because of the Cartoon Network logo), but I recently read/learned somewhere that MPG are basically designed to corrupt overtime, and presently, I can't watch ANY of those videos now on my new computer, because there's either no audio, or the video freezes up like dish does in the rain, etc.
Handbrake will rip non-protected DVDs in MP4 in decent quality (it's how I've been able to upload these SST episodes recently), yet somehow, if you download an MP4 of your own videos from your YouTube account, the download quality is really crappy.
Has this whole Google block affected Clip Converter do you know? If not, I'll give them a try to see how it compares to Zamzar.