I'm not sure about canon, but the pix220 doesn't do anything for the fs100/700. This guy did a pretty legit test doing avchd 420 24mbps vs pix220 prores 422 220mpbs and honestly you couldn't see a difference, even on the downloaded version. The only reason to ever get an external recorder is for keying or very heavy grading.
Evan Heath Visual
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"she spins left because she has no rights" - Su[G]ar[/b]