A. First, the important difference, proposability:
Because it's a MinMax method, I've had some difficulty finding a really
brief, but unambiguous definition for MMPO. MDDA has a simpler, briefer, but
still unambiguous, definition.
I still consider MMPO to be easily proposable, but MDDA seems more so.
B. Other considerations:
1. For acceptable/unacceptable situations:
When power truncation is available, both methods are equally good.
When power truncation is not available, the merit difference
depends on which kind
of voters you want to benefit. When power truncation is not
available:
In MMPO, the voter should always rank all the unacceptable
candidates in reverse
order of winnability, to maximize the votes-against of the most
winnable ones.
In MDDA, the voter should sometimes do that, but sometimes should
truncate
the unacceptables. For instance, if it's certain that the
acceptables can't beat the
unacceptables at Approval, then the only hope is to disqualify the
unacceptables,
and that goal is best helped by ranking them, in reverse order of
winnability.
The voter who is willing to strategically rank the unacceptables,
and has the
information to do so effectively is better off with MMPO, if he
doesn't have the
information to judge when to truncate in MDDA.
The voter who either doesn't have the information needed for
effective strategic
ranking, or who just doesn't intend to bother, is better off with
MDDA, because
often, maybe usually, it's better to truncate anyway.
2. Other situations other than acceptable/unacceptable:
What I said above about truncation vs strategic ranking probably
remains true even
when it isn't an acceptable/unacceptable situation.
Also, when it isn't an acceptable/unacceptable situation, it could
matter that MMPO
meets LNH, while MDDA meets SDSC. And that matters even whether
power
truncation is available or not. So the choice between LNH and SDSC
would then be
a factor in the choice between MMPO & MDDA.
Mike Ossipoff
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