- Larger battery (some people say this allows certain lenses to focus faster... not sure if this has been proven or not when compared to a gripped 5D)
Yes, this is true. With an add-on grip, the batteries are not connected in parallel, they are used alternately (you can see this from the incremental shot counts). The 1-series battery delivers a higher voltage which drives the lens' AF motor faster.
Very cool. I did not know that, but am glad to hear it.