I have 11 machines of differing speeds and processors. My question is: Why does the dual and 64 processors render about 300 mgbyts less than the single processors. IE: 2 machines dual proc, 1 64 bit single. they will render a 45min clip to 960-980 mgbyts. the 32 bit 2.2 to 3.4 gig single processors all take the same clip to 1.2gbyts . ???

That is very interesting. Can you reproduce anything like this using just transcoding clips with the ffmpeg command line utility?
Can you analyze the outputs to determine which output seems to produce the more correct result (bitrate closest to requested)?