I've stayed out of this till now but have to jump in.
Two points that  seem to have been missed in the discussion.
First, the emergence (I didn't' say origin, I don't know when they were
first used or by who) of the multi electrode spark plug was at the end
of WW2.  They were in use in aircraft to try to keep aircraft engines
running when there was oil fouling in high time engines.  They were
effective, if one electrode was fouling and resistance went up then the
spark would appear at another electrode.  But still to just ONE ground
point!  No change in 'load' on the system.
And that is the second point.  The spark is provided by the back EMF
from a collapsing field induced into the secondary winding of the coil.
It is a collapsing field because the circuit has been opened.  Any
attempt to analyze the circuit using Ohm's or Kirkoffs (sp?) law will be
wrong, there is no closed circuit at the time of the spark.  The load on
the system is solely a function of the characteristics of the primary
winding on the coil (and resistance up to that point) and has nothing to
do with whether or not the secondary is shorted to ground (through the
spark plug) or not.
The result is that the coil couldn't care less how many paths to ground
are available as long as it is discharging into the resistance it was
designed for and that is controlled by the SINGLE plug wire much more
than the configuration of the electrodes on the spark plug.
BTW, do I use multi electrode plugs?  Yes, because they should last a
little longer before needing replacement.  Do I expect better
performance? No and no reason that I should.